Why Do I Have an Armpit Rash?

An underarm rash can be uncomfortable, frustrating, and sometimes even painful. Whether your skin feels itchy, red, bumpy, or like it's burning, it's natural to wonder what's causing it, and how to make it go away.

The good news is that most underarm rashes are caused by everyday factors like friction, shaving, heat, sweat, or irritation from personal care products. In some cases, they can also be linked to skin conditions such as eczema or fungal infections.

Understanding the cause is the first step toward finding relief. In this guide, we'll cover the most common reasons for underarm irritation, how to tell them apart, and what you can do to help your skin recover.

Common Signs of an Underarm Rash

Not every underarm rash looks the same. Depending on the cause, you may notice one or more of the following:

• Redness
• Itching
• Burning or stinging
• Dry, flaky, or peeling skin
• Small bumps or blisters
• Tenderness or soreness
• Cracked skin
• Swelling
• Discoloration

If your symptoms are severe, continue to worsen, or are accompanied by fever, pus, or significant pain, it's important to seek medical advice.

What Causes an Armpit Rash?

Because the underarms are naturally warm, moist, and subject to constant movement, they're one of the easiest places for irritation to develop. Many of the instances relate to body sweat and bacteria that forms in its presence. Visit Sweat and Body Odor to learn more about this process.

Some of the most common causes include:

• Irritation from deodorant
• Allergic reactions to ingredients
• Shaving
• Heat and trapped sweat
• Friction from clothing
• Chafing
• Eczema
• Fungal or bacterial infections
• Certain medications or underlying skin conditions

Let's take a closer look at each one.

Common Types of Underarm Rashes

Not every underarm rash has the same cause. Here's a quick way to compare the most common types and what may trigger them.

Type	What It May Feel Like	Common Triggers
Contact Dermatitis	Red, itchy, inflamed, burning, dry, peeling, or tender skin.	Deodorant, fragrance, baking soda, soaps, laundry detergent, fabrics, or other irritants/allergens.
Heat Rash	Small itchy or prickly bumps, often during hot or humid weather.	Trapped sweat, heat, humidity, tight clothing, or limited airflow.
Chafing	Soreness, redness, stinging, raw skin, or discomfort where rubbing happens.	Friction from skin, clothing, sweat, moisture, or movement.
Intertrigo	Red, inflamed, moist, tender, or irritated skin in skin folds.	Skin-to-skin friction, trapped moisture, limited airflow, and sometimes yeast or bacteria.
Eczema	Dry, itchy, inflamed patches that may flare up repeatedly.	Skin sensitivity, genetics, stress, fragrances, harsh soaps, fabrics, or temperature changes.

 

Contact Dermatitis (source)

Contact dermatitis is one of the most common causes of underarm irritation. It develops when your skin reacts after coming into contact with something that either irritates it or triggers an allergic response. There are three main types of contact dermatitis that can affect the underarms.

Allergic Contact Dermatitis

Allergic contact dermatitis occurs when your immune system reacts to a specific ingredient after it comes into contact with your skin.

Common triggers include:

• Fragrance
• Essential oils
• Preservatives
• Soaps
• Laundry detergents
• Certain cosmetic ingredients

If you know you're allergic to a particular ingredient, avoiding products that contain it is the best way to prevent future reactions.

Irritant Contact Dermatitis

Unlike an allergy, irritant contact dermatitis doesn't involve your immune system. Instead, it occurs when something physically disrupts your skin barrier or changes your skin's natural pH.

One of the most common causes of irritant contact dermatitis in the underarms is deodorant.

While many people use natural deodorants without any problems, some ingredients may be irritating for sensitive skin. One common example is baking soda. Because baking soda has a naturally alkaline pH, some people find that frequent use—especially after shaving or on an already compromised skin barrier—can lead to redness, itching, burning, dryness, or peeling.

This doesn't mean natural deodorant isn't right for you. It often means your skin may simply be better suited to a different formula.

If you've experienced irritation after switching deodorants, our guide to natural deodorant for sensitive skin explains what ingredients to look for, what to avoid, and how to choose a formula that's better suited to your skin.

Common signs of irritant contact dermatitis include:

• Redness
• Dryness
• Burning
• Peeling
• Tender skin

If your deodorant is the cause, switching to a gentler formula is often enough to allow the skin to recover.

Phototoxic Contact Dermatitis

Phototoxic contact dermatitis is much less common but can occur when certain ingredients react after being exposed to sunlight.

The affected skin may become red, inflamed, and feel similar to a sunburn. While this isn't a frequent cause of underarm irritation, it's something to be aware of if symptoms appear after spending time outdoors.

Heat Rash (source)

Heat rash, also called miliaria or prickly heat, develops when sweat becomes trapped beneath the surface of the skin.

Because underarms are warm and often remain covered throughout the day, they're one of the most common places for heat rash to appear.

Symptoms often include:

• Small red bumps
• Itching
• A prickling sensation
• Mild burning
• Tender skin

Heat rash is especially common during hot weather, intense exercise, or whenever sweat can't easily evaporate.

Fortunately, it usually improves once the skin is allowed to cool and stay dry.

To help soothe heat rash:

• Wear loose, breathable clothing.
• Avoid excessive heat whenever possible.
• Apply cool compresses.
• Consider soothing ingredients like aloe vera or colloidal oatmeal.

Chafing

Sometimes an underarm rash has nothing to do with allergies or deodorant at all.

Chafing happens when skin repeatedly rubs against skin or clothing. Add moisture from sweat, and the friction can quickly lead to irritation.

Common causes include:

• Tight-fitting clothing
• Rough fabrics
• Long periods of sweating
• Exercise
• Hot weather

Chafing often starts as mild redness but can become increasingly uncomfortable if the friction continues. In more severe cases, the skin may crack or even bleed.

Choosing breathable fabrics and allowing your underarms to stay as dry as possible can help prevent future flare-ups.

Intertrigo

Intertrigo is a common skin condition that develops where skin folds rub together. Because your underarms are warm, moist, and experience constant movement, they're one of the most common places for it to occur.

The combination of trapped moisture, friction, and limited airflow can weaken the skin barrier, allowing yeast or bacteria to grow more easily.

Common symptoms include:

• Red, inflamed skin
• Burning or itching
• Tenderness
• Cracked or weeping skin
• An unpleasant odor in more severe cases

Keeping the area clean, dry, and well ventilated can often help prevent intertrigo from developing. If symptoms persist or worsen, it's important to speak with a healthcare professional, as prescription treatment may be needed.

Eczema

Eczema, also known as atopic dermatitis, is a chronic inflammatory skin condition that can affect almost any part of the body, including the underarms.

Unlike temporary irritation, eczema often comes and goes in flare-ups. The skin may become extremely itchy, dry, red, or even develop small fluid-filled bumps that can crack or ooze.

Common triggers include:

• Stress
• Dry skin
• Fragrances
• Harsh soaps
• Certain fabrics
• Changes in temperature

If you already have eczema elsewhere on your body, your underarms may simply be another area where flare-ups occur.

Managing eczema often involves avoiding known triggers, keeping the skin moisturized, and following your healthcare provider's treatment recommendations.

How to Treat an Underarm Rash at Home

The best treatment depends on what's causing the irritation. While some rashes require medical attention, many mild cases improve with a few simple changes.

Wear Breathable Clothing

Loose-fitting clothing made from natural, breathable fabrics allows air to circulate and helps reduce sweat buildup and friction.

If you exercise regularly or spend time outdoors in hot weather, changing out of damp clothing promptly can also help reduce irritation.

Avoid hot water

Although a hot shower may feel soothing, hot water can strip away the natural oils that help protect your skin.

Instead, wash your underarms with lukewarm water and a gentle cleanser. If your skin feels especially irritated, finishing with a cool rinse may provide additional relief.

Use Gentle, Soothing Ingredients

When your skin is already irritated, keeping your routine simple is often best.

Ingredients that many people find soothing include:

• Aloe vera
• Colloidal oatmeal
• Coconut oil
• Shea butter

Avoid heavily fragranced products or harsh exfoliants until your skin has recovered.

Choose a Deodorant That Works With Your Skin

If your rash appears shortly after applying deodorant, or keeps coming back in the same area, it may be worth taking a closer look at your formula.

Many people with sensitive underarms find that baking soda-free deodorants are more comfortable for everyday use while still providing reliable odor protection.

If you're trying to find a formula that's better suited to your skin, our guide to natural deodorant for sensitive skin explains what ingredients to look for, what to avoid, and how to choose a deodorant that works comfortably with your skin.

Manage stress

Stress affects more than your mood, it can also influence your skin. For people with conditions like eczema, stress may increase inflammation and contribute to flare-ups.

Finding small ways to reduce daily stress, whether that's taking a walk, reading a book, exercising, or practicing mindfulness, can benefit both your overall health and your skin.

When Should You See a Doctor?

While many underarm rashes improve with simple home care, it's important to seek medical advice if:

• Your rash lasts longer than two weeks.
• It continues to spread.
• You notice pus or drainage.
• The area becomes very painful or swollen.
• You develop a fever.
• Home treatment isn't helping.
• You're unsure what's causing the rash.

A healthcare professional can determine whether your symptoms are caused by an allergy, infection, eczema, or another underlying condition and recommend the appropriate treatment.

Most Common Questions About Underarm Rashes

Can deodorant cause an underarm rash?

Yes. Some people develop irritation or an allergic reaction to ingredients found in deodorants, including baking soda, fragrance, preservatives, or essential oils. If your rash consistently appears after applying deodorant, switching to a different formula may help.

How long does an underarm rash last?

Mild irritation often begins improving within a few days once the cause is removed. More severe rashes, infections, or eczema flare-ups may take longer and sometimes require medical treatment.

Can shaving cause an armpit rash?

Absolutely. Shaving can create tiny nicks in the skin and temporarily weaken the skin barrier, making your underarms more susceptible to irritation from sweat, friction, or deodorant.

Should I stop wearing deodorant if I have a rash?

If you suspect your deodorant is causing irritation, it's a good idea to stop using it until your skin has healed. Once the rash has resolved, choosing a gentler formula may help prevent future irritation.

Are natural deodorants better for sensitive skin?

Not all natural deodorants are the same. Some contain baking soda, while others rely on ingredients like magnesium for odor control. Many people with sensitive skin find baking soda-free formulas to be more comfortable for daily use.

Final Thoughts

An underarm rash can have many different causes, from simple friction and heat to allergies, eczema, or irritation from deodorant ingredients. Identifying what's triggering your symptoms is the first step toward helping your skin heal and preventing future flare-ups.

If your deodorant seems to be contributing to irritation, you don't necessarily have to give up on natural deodorant. Choosing a formula that's better suited to sensitive skin may make all the difference.

If you're not sure where to start, explore our guide to natural deodorant for sensitive skin to learn what ingredients to look for, what to avoid, and how to choose a formula that's gentle on your underarms while still providing reliable odor protection.

 

These statements are not intended to diagnose, treat, cure or prevent any disease. For any medical concern you should consult with an appropriately-licensed physician or other health care worker. Never disregard professional medical advice or delay in seeking it because of something you have read on this website. Full Medical Disclaimer.