Medically reviewed by Kristin Hall, FNP
Written by Our Editorial Team
Last updated 8/9/2020
Rashes are embarrassing and can be maddening. While a skin rash in, under or on your armpit might not be visible to the people around you, you know it’s there, it’s ugly and the itch is likely driving you crazy.
It’s one thing to have a medical condition such as an underarm rash; it’s another to know when it’s appropriate to see a healthcare provider about it.
Understanding some of the potential causes of your rash can help you decide if sharing your itchy little secret with a healthcare provider could provide some relief.
Spoiler: it likely would.
Dermatitis is a general, medical term for a rash, and as you might imagine, there are many types of dermatitis.
Dermatitis is red and itchy, but exact characteristics of the rash may differ by cause.
These rashes are caused by an immune response in the skin, which leads to inflammation.
The proper treatment for dermatitis depends on what’s causing the reaction.
Allergic contact dermatitis. When you have an allergic reaction to something on your skin, it’s known as allergic contact dermatitis.
Nickel allergy is one of the more common causes of allergic dermatitis, but so are poison ivy and oak.
Contact allergies generally lead to a reaction within a couple days of contact, and typically result in red, itchy skin where the allergen came in contact with the skin, as well as potential blisters and bumps.
You may spread remnants of the allergen to other areas of your body, including your armpits, with your fingers.
Mild allergic dermatitis will typically disappear within a few days or weeks, but if the rash is unbearable or lasts uncomfortably long, a healthcare provider can help determine a treatment to reduce the itching and pain.
Treatments may include: oral and topical steroids, as well as moisturizing creams.
Eczema is a type of dermatitis known as atopic dermatitis, and though it’s more common in children and adolescents, adults can have it too.
It is considered a chronic condition, and people with eczema are at a greater risk for bacterial, viral, and fungal skin infections.
Eczema rashes are very itchy and can result in dark, rough or leathery patches on the skin; oozing or crusting and swelling.
Certain environmental conditions may cause eczema flare-ups, so managing the condition is a matter of understanding what makes your eczema worse.
After diagnosis, your healthcare provider may prescribe topical or oral steroids, antihistamines, or intensive moisturizers to manage your eczema symptoms.
Dandruff is a sign of seborrhoeic dermatitis, and many people mistakenly believe it to be caused by dry skin, which leads them to try treatments that only make it worse.
Severe seborrhoeic dermatitis results in a powdery or greasy scale forming, known as erythematous plaque, which can lead to bacterial infection if untreated.
Treatment of seborrheic dermatitis involves frequent washing to remove excess oils, and also over-the-counter and prescription drugs.
Antifungal and anti-inflammatory medications may be prescribed to manage this skin condition.
Your rash could also be due to a medication you’re currently on. Adverse cutaneous drug reactions are relatively common, and some research suggests nearly half (45 percent) of adverse drug reactions are seen in the skin.
The most common skin reaction to medications are small raised bumps known as a maculopapular rash.
Drugs that commonly cause skin reactions include antimicrobials, anticonvulsants and anti-inflammatories.
Generally, treatment for drug reactions simply involves finding an alternative drug that you’re not sensitive to.
Your rash under your armpit should disappear within a week or two of stopping the medicine. Consult with a healthcare provider before stopping any medication they’ve instructed you to take.
Ringworm is an itchy fungal infection — if you’ve ever had jock itch or athlete’s foot, you’d recognize the itch.
It’s not caused by worms, though the tell-tale sign is a rash with a wavy, ring-shaped outline. Patches of ringworm are generally flat with a raised border. As they clear, the inside of the patch will clear first.
Treatment of ringworm is typically accomplished with a topical antifungal cream or ointment. The solution is applied to the affected area twice a day for a few weeks.
While over-the-counter antifungals may be effective, prescription medication may be needed for severe outbreaks.
Candida is a yeast infection that can occur on your skin.
It’s fairly common and most often occurs in warm, moist areas like your armpits.
Also known as candidiasis, this yeast infection appears as red, itchy patches of skin. They may be rimmed with small pimple-like pustules, or develop a crust.
Candida treatment involves using antifungal ointments and/or creams.
Also, because repeat infections of candida are common, keeping your skin dry can prevent the moist atmosphere it thrives in.
Lichen planus is a noncontagious rash that is believed to be caused by an overactive immune response. Hepatitis, herpes and chickenpox can trigger lichen planus development.
The rash consists of small, raised spots appearing in clusters. When they’re in the armpit, they’re commonly ring-shaped.
Lichen planus can last for years, but steroid creams can lessen the severity of the rash.
Rashes are never fun, but a rash on your armpit is a whole other level of groan.
While they may look and even feel similar, there are actually several different causes of armpit rashes, which means treatment options aren’t a “one-size-fits-all” kind of deal.
They can be a result of different fungal or bacterial infections, or can even be a side effect of — or reaction to — a medication you’re taking.
They can be a one-off case, or can be a chronic health issue. They can last for a few days, or even years if left untreated.
The point is, all of this information affects what kind of treatment options your healthcare provider is likely to recommend — from steroid creams, to antibiotics, specialized washes and everything in between.
If you’re dealing with an armpit rash and still aren’t certain what’s causing it, the best thing to do is contact your healthcare provider. They'll be able to properly diagnose just what, exactly, is causing your underarm rash, and what your best treatment options are.
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