Armpit rash can result from shaving (ingrown hair), irritant substances or allergic reaction (contact dermatitis), infection (ringworm, bacterial folliculitis, hidradenitis suppurativa), clogged sweat glands (heat rash), overactive sebaceous glands (seborrheic dermatitis) or diseases, such as diabetes or cancer (acanthosis nigricans). Armpit rashes appear on the skin surface, while armpit lumps appear beneath the skin.
Treatment of the rash depends on the cause; it can include topical or oral antibiotics, antifungals, steroids and antihistamines.
Armpit rashes presented below are divided to:
1. Red Bumps
Ingrown hair can develop after waxing, pilling or shaving, especially in people with curly hair. It appears as itchy and tender red bumps with hair arising from them .
Prevention and treatment. Avoid shaving close to the skin and unnecessary epilation. The rash can disappear on its own within several weeks . A steroid cream containing hydrocortisone, and phototherapy can reduce itching .
Picture 1. Ingrown hair (source: Samuel Freire da Silva, M.D., Atlasdermatologico.com.br)
1.2. Bacterial Folliculitis
Bacterial folliculitis is an infection of the hair follicles, usually by the bacterium Staphylococcus aureus. It appears as multiple itchy or burning red acne-like pimples with white pus-filled centers . It can result from bad hygiene, sharing the gym equipment, the friction of tight clothes or frequent shaving.
Treatment is with an ointment containing the antibiotic erythromycin or mupirocin .
Picture 2. Bacterial folliculitis (source: Samuel Freire da Silva, M.D., Atlasdermatologico.com.br)
1.3. Heat Rash
Heat rash (sweat rash, prickly heat, miliaria) appears as small translucent itchy or burning blisters, red, shallow bumps (papules), goose bumps-like rash or deep lumps . It is triggered by sweating. It can heal on its own in several weeks .
Treatment is by avoiding sweating and skin irritation, by calamine lotion or steroid creams .
Picture 3. Sweat rash or miliaria (source: Samuel Freire da Silva, M.D., Atlasdermatologico.com.br)
1.4. Hidradenitis Suppurativa
Hidradenitis suppurativa (acne inversa) is a chronic inflammation of the hair follicles in the armpits (or under the breasts or in the groin) that may develop after puberty, especially in obese people. Symptoms include painful red pimples and lumps (abscesses or swollen lymph glands) that may rupture and ooze foul-smelling fluid and eventually scar over . Treatment can include topical or oral antibiotics, retinoids, infliximab and surgical removal of the affected skin .
Picture 4. Hidradenitis suppurativa (source: Samuel Freire da Silva, M.D., Atlasdermatologico.com.br)
1.5. Fox-Fordyce Disease
In a rare “sweat retention disease” or Fox-Fordyce disease, mainly in the females between 13 and 35 years of age, blockage of the sweat glands can result in red bumps, severe itch and decreased sweating in the armpits, around the nipples and in the pubic area . Treatment can include topical retinoids, steroids and antibiotics .
2. Scaly Patches
Ringworm is a fungal skin infection caused by Tinea axillaris. It appears as red or brown and scaly patches in the form of circles or rings [3,4]. Risk factors include diabetes mellitus and moist skin.
Treatment: topical or oral antifungals.
Picture 5. Ringworm (source: Samuel Freire da Silva, M.D., Atlasdermatologico.com.br)
2.2. Contact Dermatitis
- Irritant contact dermatitis appears as itchy red, dry, scaly or peeling patches with possible cracks (eczema) .
- Allergic contact dermatitis appears as itchy pink blisters or patches (hives or urticaria) .
Treatment of irritant contact dermatitis can include moisturizing or steroid creams . Treatment of allergic contact dermatitis can include topical or oral steroids or antihistamines, and tacrolimus or pimecrolimus ointments [11,12].
Picture 6. Contact dermatitis (source: Samuel Freire da Silva, M.D., Atlasdermatologico.com.br)
2.3. Inverse Psoriasis
Treatment is with steroid ointments, calcipotriene, coal tar or anthralin .
Picture 7. Inverse psoriasis (source: Intechopen, Creative Commons license)
Erythrasma is a chronic skin infection caused by the bacteria Corynebacterium. It appears with sharply outlined red or brown scaly patches in the armpits or groin . The rash is rarely itchy . Risk factors include moist environment, diabetes and obesity.
Photodynamic therapy can clear or reduce the rash .
Picture 8. Erythrasma (source: Samuel Freire da Silva, M.D., Atlasdermatologico.com.br)
2.5. Seborrheic Dermatitis
Seborrheic dermatitis appears as scaly skin-colored or red patches on the scalp (with dandruff), face, armpits and groin in some people with oily skin. The condition develops due to an increased activity of the sebaceous glands and associated fungal infection . Treatment can include ointments with salicylic acid, antifungals, steroids, pimecrolimus or tacrolimus .
2.6. Hailey-Hailey Disease
Treatment can include topical steroids, antibiotics and benzoyl peroxide .
Picture 9. Hailey-Hailey disease (source: Wikipedia, Creative Commons license)
Intertrigo is a general term for inflamed skin in the body folds, such as under the arms and breasts or in the groin [1,2]. It appears as itchy or burning red or brown patches that are moist and can peel off [1,2]. Risk factors include genetic predisposition, obesity and hyperhidrosis .
3. Dark Rashes (Hyperpigmentations)
3.1. Acanthosis Nigricans
Acanthosis nigricans refers to a thick dark skin on the back of the neck, in the armpits and groin in certain conditions, such as obesity, diabetes mellitus, stomach or other cancer, or as a side effect of drugs (nicotinic acid, insulin, corticosteroids, hormones) . The rash is rarely itchy and can disappear after treatment of the underlying condition.
Treatment of the rash itself may not be very effective but can include triple-combination depigmenting cream (tretinoin, hydroquinone, fluocinolone acetonide) or oral drugs, such as etretinate and isotretinoin .
Picture 10. Acanthosis nigricans (source: Dr. Fedro Portugal, Atlasdermatologico.com.br)
4. Skin Tags
A skin tag (acrochordon) is a piece of skin in the form of “stalk” or “berry” that freely hangs down. Skin tags can be skin-colored or dark brown and are usually painless and harmless. A doctor can tell if there is any danger of development into cancer.
Picture 11. Skin tags (source: Wikipedia, Creative Commons license)
Prevention and Home Remedies
- Wear loose, airy clothes, heat and excessive alcohol drinking to avoid moist in armpits.
- Avoid deodorants, antiperspirants and armpit shaving.
- Do not scratch, if possible, at least not with the nails.
- To reduce itch–only when the skin is not cracked–you can apply :
- Moist cold dressing (for eczema)
- Moist warm dressing (for ingrown hair, folliculitis)
- Baking soda paste
- Calamine lotion (for hives, not for dry skin) 
- Colloidal oatmeal (for eczema)
- Menthol/camphor lotion
- Moisturizing creams or emollients (for dry skin eczema)
- Armpit conditions WebMD
- Scheinfeld NS, Cutaneous candidiasis clinical presentation Emedicine
- Bell SA et al, 1996, Tinea axillaris, a variant of intertriginous tinea, due to non-occupational infection with Trichophyton verrucosum PubMed
- Tinea infections MedlinePlus
- Hidradenitis suppurativa signs and symptoms American Academy of Dermatology
- Fox-Fordyce disease DermNet NZ
- Miliaria DermNet NZ
- Ngan V, Acanthosis nigricans DermNet NZ
- Oakly A, Folliculitis barbae and pseudofolliculitis barbae DermNet NZ
- Irritant contact dermatitis DermNet NZ
- Allergic contact dermatitis DermNet NZ
- Hogan DJ, Allergic contact dermatitis Emedicine
- Intertrigo DermNet NZ
- Seborrheic dermatitis DermNet NZ
- Acanthosis nigricans treatment and management Emedicine
- Miliaria DermNet NZ
- Hidradenitis suppurativa, treatment Mayo Clinic
- Topical steroids DermNet NZ
- Bacterial folliculitis DermNet NZ
- Kibbi AG, Erythrasma clinical presentation Emedicine
- Kibbi AG, Erythrasma treatment Emedicine
- Hailey-Hailey disesae DermNet NZ
- Calamine lotion Drugs.com
- Itch, pruritus Dermenet NZ
- Inverse psoriasis National Psoriasis Foundation