Skin Diseases
Skin cancer is the most common type of cancer worldwide, affecting millions of people each year. It occurs when abnormal skin cells grow uncontrollably, often due to damage from ultraviolet (UV) radiation. While skin cancer can be life-threatening if left untreated, it is also one of the most...
Constant lip licking strips the natural barrier, causing a red, chapped ring around the lips that stings and burns—especially in cold weather. How it looks Red, dry, sometimes shiny or scaly skin...
A scaly hand rash can be fungus (tinea manuum) or eczema. Getting it right matters because treatments differ. Tinea Manuum (Fungal Hand Infection) Clues it’s fungus: Usually one hand worse than the...
Dyshidrotic eczema causes sudden crops of very itchy, tiny, deep “tapioca” blisters on sides of fingers, palms, and soles. It flares with stress, sweat, nickel sensitivity, or seasonal changes. Signs...
Chilblains are small, itchy, painful red-purple patches on fingers or toes after exposure to cold, damp conditions. They’re due to abnormal small-vessel reactions—not frostbite—and usually resolve in...
Hyperhidrosis is sweating beyond what’s needed for cooling—commonly palms, soles, underarms, and face. It’s not dangerous, but it can impact daily life. Treatments work best when stepped up...
“Maskne” is acne and irritation triggered by mask friction, heat, sweat, and trapped humidity. How it shows up Blackheads/whiteheads, red inflamed bumps where the mask sits (nose bridge, cheeks...
Scalp itch can come from flakes (dandruff) or inflamed hair follicles (folliculitis). Knowing the difference guides treatment. Dandruff (Seborrheic Dermatitis) What it looks like: White/yellow flakes...
Friction plus sweat causes chafing and intertrigo in runners, cyclists, hikers, and gym-goers. Quick steps can prevent pain and speed recovery. Chafing (Friction Rash) Where: Inner thighs, underarms...
Light patches on a child’s face or body can be worrying. Two common causes are pityriasis alba and vitiligo. Here’s how to tell them apart and what to do. Pityriasis Alba (PA) Who: School-age kids...
Cold, dry air strips moisture from skin, leading to flares of eczema and painful chapping. A few tweaks to routine make a big difference. Everyday winter routine Short, lukewarm showers (5–10...
Tinea versicolor is a common superficial yeast overgrowth on the skin that causes light or dark patches, often on the chest, back, shoulders, and neck. It tends to recur, especially in warm, humid...
Perioral dermatitis causes small red bumps around the mouth, nose, and sometimes eyes. It’s common, especially in women, and often triggered by topical steroids or heavy face products. What it looks...
HS is a chronic inflammatory skin condition causing tender lumps, boils, and tunnels in areas with friction and apocrine glands—most often armpits, groin, under breasts, buttocks, and inner thighs...
Keratosis pilaris causes small, rough bumps often on the upper arms, thighs, buttocks, and cheeks. It’s harmless and common, especially in kids and teens, and tends to improve with age. What it...
Razor bumps and ingrown hairs happen when shaved hairs curl back into the skin or get trapped under the surface, causing bumps and irritation. Common on beard area, neck, bikini line, underarms, and...
Most teen acne can be managed at home with a steady routine. Expect 8–12 weeks to see strong improvement. Basics that work Wash face twice daily and after sports with a gentle, non-comedogenic...
Hand eczema is common in school-aged children, especially with frequent handwashing and sanitizer use. Good routines prevent cracks and infections. How it looks Dry, rough, red patches on backs of...
Painful cracks at one or both corners of a child’s mouth. Often due to saliva irritation and yeast (Candida) overgrowth. Common with drooling, lip licking, thumb sucking, braces, or chapped lips...
These can all cause a flaky scalp in children. Here’s how to tell them apart and what to do. Cradle Cap (Infant Seborrheic Dermatitis) Who: Mostly 0–12 months. Look: Greasy yellow scales stuck to...
MRSA (methicillin-resistant Staph aureus) is a common cause of skin infections like boils and abscesses. It spreads easily with close contact but simple steps cut the risk. How it spreads Skin-to-skin...
Lichen sclerosus (LS) is a long-term inflammatory skin condition that can affect the genitals. In men, it most often involves the foreskin and head of the penis (glans) and can scar over time. It’s...
Eczema is a common, itchy skin condition in kids. The skin barrier is sensitive and dries out easily, leading to redness and itch. Good routines calm flares and prevent new ones. How it looks Dry...
Understanding common skin spots helps you know when to relax and when to get checked. Sunspots (Lentigines, “Age Spots”) What they are: Flat, light- to dark-brown spots caused by sun exposure over...
Body odor comes from sweat interacting with skin bacteria. It’s normal to have some odor, but strong or persistent smells can be improved with targeted care. Types of sweat Eccrine sweat: watery, all...
These are common, contagious fungal rashes that thrive in warmth and moisture. They often occur together (“two-foot–one-groin” syndrome). Athlete’s Foot (Feet) What it looks like Itchy, burning...
What it is An allergic skin reaction to urushiol oil in poison ivy, oak, and sumac. The rash is not contagious, but the oil can spread from plants, pets, tools, or clothing. How exposure happens...
Sunburn What it is Skin damage from too much ultraviolet (UV) radiation from the sun or tanning beds. It can range from mild redness to painful blistering. Symptoms Red, warm, tender skin 2–6 hours...
Diaper rash is irritation of the skin under a diaper. It’s very common and usually easy to treat. Moisture, friction, and contact with urine/stool break down the skin barrier; yeast can overgrow and...
Cradle cap is a common, harmless skin condition in babies that causes greasy, yellow scales on the scalp. It isn’t contagious, doesn’t itch much, and usually clears on its own within weeks to months...
Angular cheilitis is inflammation and painful cracks at one or both corners of the mouth. It’s often due to moisture and irritation, with yeast (Candida) or bacteria contributing. Why it happens...
These two mouth problems are often confused but have different causes and care. Canker sores (Aphthous ulcers) What they are: Small, shallow ulcers inside the mouth (inner lips/cheeks, tongue, soft...
These three can all cause a flaky or scaly scalp, but they differ in cause and treatment. Dandruff (Seborrheic Dermatitis of the Scalp) What it is: A common, noncontagious condition linked to skin...
An ingrown toenail happens when the corner or side of a toenail grows into the nearby skin, causing pain, redness, swelling, and sometimes infection. The big toe is most often affected. Why it happens...
Part A: Sun Safety Essentials Why it matters Sun exposure ages skin (wrinkles, spots) and raises risk of skin cancer (including melanoma). Protection works at any age. Sun-smart steps Seek shade from...
Hand dermatitis is irritation or eczema on the hands caused by frequent wet work, soaps/chemicals, gloves, or allergens at home or work. It leads to dry, cracked, itchy, sometimes painful skin. It’s...
Syphilis is a sexually transmitted infection caused by the bacterium Treponema pallidum. It has stages, and skin signs are common early on. It’s curable with antibiotics, but early diagnosis matters...
Genital warts are soft, flesh-colored or pink growths caused by certain types of human papillomavirus (HPV), usually types 6 and 11. They’re common, benign, and treatable—but can recur. How they...
Genital herpes is a common sexually transmitted infection (STI) caused by herpes simplex virus (HSV-1 or HSV-2). It can cause painful blisters or sores, but many people have very mild symptoms or none...
Roseola is a common viral illness in babies and toddlers (usually 6–24 months). It typically causes a sudden high fever for a few days, followed by a pink rash once the fever breaks. Most children...
Rubella is a contagious viral illness that is usually mild in children and adults, with low fever, swollen lymph nodes, and a fine pink rash. It is dangerous in pregnancy because it can harm a...
Measles is a highly contagious viral illness. It causes high fever, cough, runny nose, red eyes, and a spreading red rash. Vaccination protects very well. How it spreads Through the air by coughs and...
An early sign of Lyme disease, caused by a tick bite (blacklegged/deer tick). The first symptom is often a spreading red rash called erythema migrans. Where it happens Common in certain regions (parts...
A skin abscess (boil) is a pocket of pus under the skin, usually from a bacterial infection. “Community MRSA” (CA-MRSA) is a common cause—it’s a type of Staph bacteria that’s harder to treat with some...
Intertrigo is an irritation and rash in skin folds (under breasts, groin, belly folds, between buttocks, between toes). Warmth and moisture allow yeast (Candida) to overgrow, causing a red, sore...
Lichen sclerosus (LS) is a long-term inflammatory skin condition that mainly affects the genital and anal area. It makes the skin thin, fragile, and itchy. It’s not contagious. With proper treatment...
Round, coin-shaped patches of eczema that are very itchy. Often on arms and legs. Triggers Dry skin, winter weather, harsh soaps, skin injuries (scratches, insect bites). Symptoms Round, scaly, red or...
An itchy hand/foot eczema with tiny, deep “tapioca-like” blisters on the sides of fingers, palms, and soles. Triggers Stress, sweat, heat, nickel or other metal exposure (jewelry, keys), detergents...
A harmless yeast overgrowth on the skin that causes lighter or darker patches, often on the chest, back, or shoulders—more noticeable after sun exposure. Symptoms Flat patches that are lighter or...
A contagious fungal infection of the scalp and hair shafts. It’s common in school-age kids and causes scaly patches, hair loss, and sometimes swollen lymph nodes. How it spreads Close contact, shared...
Shingles is a reactivation of the same virus that causes chickenpox. It causes a painful, blistering rash on one side of the body or face, usually in a stripe along a nerve (a “dermatome”). It’s more...
Chickenpox is a very contagious viral illness that causes an itchy, blister-like rash, fever, and tiredness. It’s usually mild in healthy children but can be serious in babies, adults, pregnant...
Skin tags (acrochordons) Small, soft, skin-colored flaps on the neck, armpits, eyelids, and groin. Harmless and very common, especially with age, friction, pregnancy, and in people with insulin...
Warts are small, harmless skin growths caused by human papillomavirus (HPV). They’re very common, especially in kids and teens. They often go away on their own but can take months to years. How you...
Fifth disease is a common childhood illness caused by parvovirus B19. It’s best known for a “slapped cheek” facial rash and a lacy pink rash on the body. Most cases are mild. What causes it and how it...
Hand-Foot-and-Mouth Disease is a very common, contagious viral illness, mostly in young children. It’s usually mild. It causes small blisters or spots on the hands, feet, and inside the mouth, and...
Systemic sclerosis (SSc) is a multisystem autoimmune disease characterized by vasculopathy, immune activation, and fibrosis affecting skin and internal organs. Cutaneous involvement defines two main...
Morphea is an autoimmune, inflammatory disorder characterized by excessive collagen deposition leading to localized skin induration and sclerosis without internal organ involvement (distinguishing it...
Pyogenic granuloma is a common benign vascular proliferative lesion presenting as a rapidly growing, friable red papule or polyp that bleeds easily. Despite the name, it is neither pyogenic nor...
Infantile hemangiomas are common benign vascular tumors of infancy characterized by a proliferative phase in early infancy followed by gradual involution over years. Most are uncomplicated and require...
Pitted keratolysis is a superficial bacterial infection of the stratum corneum on weight-bearing areas of the soles (and less commonly palms) characterized by malodor and discrete crateriform pits. It...
Erythrasma is a superficial bacterial infection of the stratum corneum caused by Corynebacterium minutissimum. It presents as well-demarcated, brownish-red patches in intertriginous areas with fine...
Epidermal inclusion cysts are common benign intradermal cysts lined by stratified squamous epithelium and filled with keratin. They present as slow-growing, firm, dome-shaped nodules with a central...
Lipomas are common benign tumors composed of mature adipocytes, usually presenting as soft, mobile, painless subcutaneous nodules on the trunk, shoulders, neck, or extremities. Most are solitary and...
Sézary syndrome is an aggressive leukemic variant of CTCL characterized by erythroderma, generalized lymphadenopathy, and malignant T‑cell (Sézary cell) circulation. It carries a poorer prognosis than...
Mycosis fungoides is the most common primary cutaneous T‑cell lymphoma (CTCL), typically an indolent CD4+ epidermotropic malignancy presenting with patches and plaques on sun-protected sites. Disease...
Dermatofibromas are common benign dermal proliferations, often presenting as firm papules or nodules on the extremities of young to middle-aged adults. They are usually asymptomatic but may be...
Seborrheic keratoses are common, benign epidermal tumors that present as well-demarcated, “stuck-on,” waxy papules or plaques with variable pigmentation. They arise in adulthood and increase with age...
Merkel cell carcinoma is a rare, aggressive neuroendocrine skin cancer with high propensity for local recurrence and early metastasis. It is associated with Merkel cell polyomavirus (MCPyV)...
Cutaneous melanoma is a malignant tumor of melanocytes with high metastatic potential. Incidence has risen globally, though mortality has improved with earlier detection and effective systemic...
Cutaneous squamous cell carcinoma arises from keratinocytes due to cumulative UV damage and other carcinogens. It ranges from low-risk lesions curable with excision to high-risk tumors with metastatic...
Basal cell carcinoma is the most common human malignancy, arising from basal keratinocytes with strong links to UV exposure and PTCH1/HH pathway dysregulation. It grows slowly with rare metastasis but...
Pediculosis refers to infestation by blood-sucking lice: Pediculus humanus capitis (head lice), P. humanus humanus (body lice), and Pthirus pubis (pubic or crab lice). Head lice are common in...
Scabies is a pruritic infestation by the mite Sarcoptes scabiei var. hominis. Transmission is primarily via prolonged skin-to-skin contact; fomites can spread crusted scabies. Classic scabies presents...
Tinea corporis is a superficial dermatophyte infection of glabrous skin caused by Trichophyton, Microsporum, or Epidermophyton species. It presents as annular erythematous plaques with advancing scaly...
Tinea pedis is a dermatophyte infection of the feet, most commonly caused by Trichophyton rubrum. Clinical patterns include interdigital maceration, moccasin (hyperkeratotic) scale, and...
Cutaneous HSV infections present as grouped vesicles on an erythematous base with burning pain, evolving to erosions and crusts. HSV-1 commonly affects orolabial areas; HSV-2 is more often genital...
Herpes zoster is a reactivation of latent varicella-zoster virus (VZV) in sensory ganglia, producing a unilateral, dermatomal vesicular eruption with neuropathic pain. Complications include...
Cellulitis is an acute bacterial infection of the dermis and subcutaneous tissue presenting with warmth, erythema, edema, and tenderness; erysipelas is a more superficial variant with raised, sharply...
Impetigo is a highly contagious superficial bacterial skin infection, most commonly affecting children. Nonbullous impetigo presents with honey-colored crusts on an erythematous base, typically caused...
Common warts are benign epidermal proliferations caused by cutaneous human papillomaviruses (HPV), most often types 1, 2, 4, 27, and 57. They present as hyperkeratotic papules with thrombosed...
Molluscum contagiosum (MC) is a common, self-limited poxvirus infection presenting as dome-shaped, umbilicated papules. It spreads via skin-to-skin contact, fomites, and autoinoculation. Disease is...
Onycholysis is distal separation of the nail plate from the nail bed, producing a white/opaque area that may accumulate secondary debris and pigment. It is a sign, not a diagnosis, with diverse causes...
Paronychia is inflammation of the periungual folds. Acute paronychia is a rapid-onset bacterial infection (usually Staphylococcus aureus; occasionally streptococci or oral anaerobes in nail-biters)...
Nail psoriasis affects up to 50% of patients with cutaneous psoriasis and is a strong risk factor for psoriatic arthritis (PsA). Matrix involvement causes pitting, leukonychia, crumbling; nail bed...
Onychomycosis is a fungal infection of the nail unit caused by dermatophytes (most commonly Trichophyton rubrum), yeasts, or non-dermatophyte molds, leading to onycholysis, subungual hyperkeratosis...
Telogen effluvium is a non-scarring diffuse hair shedding disorder caused by a shift of hair follicles from anagen to telogen, leading to increased daily shedding. It can be acute (≤6 months) or...
Androgenetic alopecia is the most common non-scarring hair loss, characterized by progressive miniaturization of hair follicles in androgen-sensitive scalp regions. Men show bitemporal recession and...
Alopecia areata is a non-scarring, autoimmune hair loss disorder characterized by sudden, well-circumscribed patches of hair loss that can progress to total scalp (AT) or universal body hair loss...
Post-inflammatory hyperpigmentation is an acquired hypermelanosis that follows cutaneous inflammation or injury. It is highly prevalent in skin of color (Fitzpatrick IV–VI) and can be epidermal...
Vitiligo is an acquired depigmenting disorder characterized by destruction or functional loss of melanocytes, resulting in well-demarcated depigmented macules and patches. Autoimmunity, oxidative...
Dermatitis herpetiformis is a chronic, intensely pruritic, blistering disorder associated with gluten-sensitive enteropathy (celiac disease). It presents with grouped vesicles and excoriated papules...
Mucous membrane pemphigoid (MMP), also called cicatricial pemphigoid, is a chronic autoimmune subepidermal blistering disorder primarily affecting mucous membranes with a tendency toward scarring...
Bullous pemphigoid is the most common autoimmune subepidermal blistering disorder of older adults, characterized by tense bullae on erythematous or urticarial bases and severe pruritus. Autoantibodies...
Pemphigus vulgaris is a life-threatening autoimmune blistering disease characterized by flaccid intraepidermal bullae and erosions of skin and mucous membranes due to IgG autoantibodies against...
Periorificial dermatitis (POD) is an inflammatory facial eruption characterized by grouped erythematous papules/pustules and background erythema around the mouth, nose, and/or eyes, often sparing the...
Rosacea is a chronic inflammatory facial dermatosis with four main phenotypes: erythematotelangiectatic (ETR), papulopustular (PPR), phymatous (including rhinophyma), and ocular rosacea...
Acne vulgaris is a common chronic disorder of the pilosebaceous unit characterized by comedones, inflammatory papules/pustules, and nodules that can lead to scarring and dyspigmentation. Pathogenesis...
Pyoderma gangrenosum is a rare, neutrophilic dermatosis presenting as rapidly progressive, painful ulcers with undermined violaceous borders. Pathergy is characteristic. PG is frequently associated...
Hidradenitis suppurativa (HS) is a chronic, relapsing inflammatory disease of hair follicles in intertriginous regions, characterized by painful nodules, abscesses, double-ended comedones, sinus...
Sarcoidosis is a multisystem granulomatous disease characterized by noncaseating granulomas. Cutaneous sarcoidosis occurs in up to one-third of patients and may be the initial or sole manifestation...
Cutaneous vasculitis encompasses a spectrum of disorders characterized by vessel wall inflammation resulting in purpura, nodules, ulcers, and livedoid changes. Small-vessel neutrophilic...
Dermatomyositis (DM) is an idiopathic inflammatory myopathy characterized by pathognomonic cutaneous findings and variable muscle, lung, and systemic involvement. Cutaneous dermatomyositis (CDM) may...
Cutaneous lupus erythematosus (CLE) encompasses a spectrum of lupus-specific skin diseases that may occur with or without systemic lupus erythematosus (SLE). Major subtypes include acute CLE (ACLE)...
Erythema multiforme (EM) is an acute, immune-mediated eruption characterized by target lesions, commonly triggered by herpes simplex virus (HSV). Stevens–Johnson syndrome (SJS) and toxic epidermal...
Urticaria (hives) consists of transient, pruritic wheals with or without angioedema due to mast cell activation and histamine release. It is classified by duration into acute (<6 weeks) and chronic...
Pityriasis rosea (PR) is a self-limited papulosquamous eruption characterized by a herald patch followed by a secondary exanthem of oval, erythematous plaques with collarette scale along cleavage...
Lichen planus (LP) is a chronic, inflammatory, papulosquamous disorder affecting skin, mucous membranes, hair, and nails. It presents most commonly with pruritic, flat-topped, violaceous papules and...
Psoriasis is a chronic, immune-mediated disease characterized by well-demarcated, erythematous plaques with silvery scale, driven primarily by the IL-23/Th17 axis. It affects skin, nails, scalp...
Seborrheic dermatitis (SD) is a chronic, relapsing inflammatory dermatosis affecting sebaceous-rich areas (scalp, face, chest), characterized by erythematous plaques with greasy scale and pruritus of...
Contact dermatitis (CD) is an eczematous reaction of the skin triggered by exogenous agents via two principal mechanisms: irritant contact dermatitis (ICD) due to direct cytotoxicity, and allergic...
Atopic dermatitis (AD) is a chronic, relapsing inflammatory skin disease characterized by pruritus, eczematous lesions, and a disrupted skin barrier. It arises from a multifactorial interplay of...