Pain Under Your Right Armpit? Cysts, Lymph Nodes, and Strains Explained

Experiencing pain under your right armpit can feel worrying. The armpit (also called the axilla) is a small space, but it contains important structures—muscles, lymph nodes, nerves, sweat glands, and hair follicles. Because of this, several different conditions can cause discomfort in this area.

The good news? Most causes are not serious and improve with simple care. However, some situations do require medical attention. Below, we'll walk through the most common reasons for pain under the right armpit, what symptoms to look for, and when to see a doctor.

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Common Causes of Pain Under Right Armpit

1. Muscle Strain or Overuse

One of the most frequent causes of pain under right armpit is a muscle strain. The chest muscles (pectorals), shoulder muscles, and upper arm muscles all connect near the armpit.

You may have strained a muscle if:

• You recently lifted heavy objects
• You started a new workout
• You did repetitive arm movements (painting, throwing, pushing)
• The pain worsens when you move your arm or shoulder
• The area feels sore but not swollen

Muscle strain pain is usually:

• Dull, aching, or tight
• Worse with movement
• Better with rest

What helps:

• Resting the arm
• Ice for the first 24–48 hours
• Over-the-counter anti-inflammatory medication (if safe for you)
• Gentle stretching once pain improves

Most mild strains improve within 1–2 weeks.

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2. Swollen Lymph Nodes

Your armpit contains many lymph nodes. These small glands help your body fight infection. When you're sick or fighting inflammation, they can swell and become tender.

Common reasons for swollen lymph nodes include:

• Colds or flu
• Skin infections
• Shaving irritation
• Cuts on the arm or hand
• Viral illnesses

Swollen lymph nodes often feel:

• Like small, movable lumps
• Tender to the touch
• Slightly firm

If the pain under right armpit is caused by swollen lymph nodes, you may also notice:

• Fever
• Fatigue
• Sore throat
• Signs of infection elsewhere

Most swollen lymph nodes shrink within 1–2 weeks once the infection clears.

When to See a Doctor About Lymph Nodes

Seek medical advice if:

• The lump lasts more than 2–4 weeks
• It continues growing
• It feels very hard or fixed in place
• You have unexplained weight loss
• You experience night sweats or persistent fever

While rare, persistent enlarged lymph nodes can sometimes signal more serious conditions, including certain cancers. It's important not to ignore long-lasting swelling.

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3. Cysts and Abscesses

Another common cause of pain under right armpit is a cyst or abscess.

Sebaceous (Epidermoid) Cysts

These are small, slow-growing lumps under the skin. They form when a hair follicle or oil gland becomes blocked.

They may:

• Feel round and smooth
• Move slightly under the skin
• Become tender if inflamed

Most cysts are harmless. However, if they become infected, they may turn red, warm, and painful.

Abscess

An abscess is a pocket of infection filled with pus. It can develop from:

• Shaving cuts
• Ingrown hairs
• Bacterial skin infections
• Blocked sweat glands

Symptoms of an abscess:

• Increasing pain
• Swelling
• Redness
• Warm skin
• Possible fever

Abscesses often require medical treatment and sometimes drainage by a healthcare professional. Do not try to squeeze or pop one yourself.

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4. Hidradenitis Suppurativa (HS)

Hidradenitis suppurativa is a chronic skin condition that commonly affects the armpits.

It causes:

• Painful lumps under the skin
• Recurrent boils
• Drainage
• Scarring over time

HS tends to:

• Come and go
• Affect both armpits
• Start after puberty

If you have repeated painful lumps in your right armpit, especially if they leave scars, talk to a doctor. Early treatment can reduce flare-ups and discomfort.

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5. Shaving Irritation or Ingrown Hairs

The skin in your armpit is sensitive. Shaving, waxing, or using certain deodorants can cause:

• Razor burn
• Small red bumps
• Ingrown hairs
• Mild pain or itching

Pain under the right armpit from shaving is usually mild and improves within a few days.

To prevent irritation:

• Use a clean, sharp razor
• Shave in the direction of hair growth
• Use shaving cream
• Avoid heavily scented deodorants if sensitive

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6. Nerve-Related Pain

Sometimes pain under right armpit isn't from the skin or lymph nodes at all. It may be nerve-related.

Possible causes:

• Pinched nerve in the neck
• Poor posture
• Shoulder injuries

Nerve pain may feel:

• Sharp or burning
• Tingling or numb
• Radiating down the arm

If you also have weakness or persistent numbness, consult a healthcare provider.

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7. Breast-Related Causes (In Women)

In women, some breast tissue extends into the armpit area. Conditions that may cause pain under right armpit include:

• Hormonal breast tenderness
• Breast cysts
• Mastitis (infection)
• Rarely, breast cancer

Signs that need medical evaluation:

• A hard lump that doesn't move
• Skin dimpling
• Nipple discharge
• Persistent one-sided swelling

Breast cancer is not a common cause of armpit pain by itself—but any unexplained lump should be evaluated promptly.

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When Is Pain Under Right Armpit Serious?

Most cases are mild and temporary. However, you should speak to a doctor immediately if you have:

• Severe or worsening pain
• High fever
• Rapid swelling
• Red streaks spreading from the area
• Chest pain or shortness of breath
• A lump that doesn't go away after several weeks
• Unexplained weight loss

These symptoms could indicate a serious infection or another significant medical condition.

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What You Can Do Now

If your symptoms are mild, you can try:

• Resting your arm
• Applying ice (10–15 minutes at a time)
• Wearing loose clothing
• Avoiding shaving temporarily
• Monitoring the area for changes

If you're unsure what's causing your discomfort or need help identifying whether your symptoms require professional evaluation, try using a free AI-powered arm pain symptom checker to get personalized insights and guidance on next steps.

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The Bottom Line

Pain under right armpit is usually caused by:

• Muscle strain
• Swollen lymph nodes
• Cysts or abscesses
• Skin irritation
• Minor infections

Most cases improve with rest and basic care. However, persistent lumps, worsening pain, fever, or other unusual symptoms should never be ignored.

If your pain lasts more than a couple of weeks, keeps returning, or concerns you in any way, speak to a doctor. Some causes—such as deep infections or cancer—can be serious or even life-threatening if left untreated. Early evaluation leads to better outcomes.

Listen to your body. Mild symptoms often pass. Persistent or severe ones deserve medical attention.