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Bump on the Bicep or Tricep Symptom, Causes & Questions

An illustration of a person's flexed right arm. Their skin is medium peach-toned and there is a red bump on the bottom of the upper arm. Red translucent concentric circles come from the bump.
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Last updated March 7, 2024

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Bumps on the upper arms are usually caused by common conditions such as skin cysts or pimples, though it's important to talk to your doctor to identify the cause and get the right treatment. Read more below to learn 9 possible causes of bumps on the upper arm.

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9 causes of bumps on the bicep or tricep

This list does not constitute medical advice and may not accurately represent what you have.

Wart

Warts, also called common warts or verrucae, are small, rough, rounded growths on the top layer of the skin. They may appear singly or in clusters.

Common warts are caused by the human papilloma virus (HPV) and are contagious through direct contact, especially through a break in the skin. They may spread from one place on the body to another simply through touch.

Anyone can get warts but they are most common in anyone with a weakened immune system, as from illness or chemotherapy. Children and teenagers are also susceptible to warts.

Warts often first appear on the hands and fingers, especially near the nails or after any injury to the skin. This is why biting fingernails is a risk factor for warts.

Warts are benign, meaning they are not cancerous. But they can be unsightly and interfere with normal use of the hands, so treatment is often beneficial.

Diagnosis is made through physical examination. Warts in children sometimes go away without treatment, but otherwise most warts can be easily removed in a doctor's office.

Skin cyst

A cyst is a small sac or lump, filled with fluid, air, fat, or other material, that begins to grow somewhere in the body for no apparent reason. A skin cyst is one that forms just beneath the skin.

It's believed that skin cysts form around trapped keratin cells – the cells that form the relatively tough outer layer of the skin.

These cysts are not contagious.

Anyone can get a skin cyst, but they are most common in those who are over age 18, have acne, or have injured the skin.

Symptoms include the appearance of a small, rounded lump under the skin. Cysts are normally painless unless infected, when they will be reddened and sore and contain pus.

Diagnosis is made through physical examination. A small cyst can be left alone, though if it is unsightly or large enough to interfere with movement it can be removed in a simple procedure done in a doctor's office. An infected cyst must be treated so that the infection does not spread.

Rarity: Common

Top Symptoms: skin-colored armpit bump, marble sized armpit lump, small armpit lump

Symptoms that always occur with skin cyst: skin-colored armpit bump

Urgency: Wait and watch

Skin abscess

A skin abscess is a large pocket of pus that has formed just beneath the skin. It is caused by bacteria getting under the skin, usually through a small cut or scratch, and beginning to multiply. The body fights the invasion with white blood cells, which kill some of the infected tissue but form pus within the cavity that remains.

Symptoms include a large, red, swollen, painful lump of pus anywhere on the body beneath the skin. There may be fever, chills, and body aches from the infection.

If not treated, there is the risk of an abscess enlarging, spreading, and causing serious illness.

Diagnosis is made through physical examination.

A small abscess may heal on its own, through the body's immune system. But some will need to be drained or lanced in a medical provider's office so that the pus can be cleaned out. Antibiotics are usually prescribed.

Keeping the skin clean, and using only clean clothes and towels, will help to make sure that the abscess does not recur.

Rarity: Common

Top Symptoms: rash with bumps or blisters, red rash, red skin bump larger than 1/2 cm in diameter, pus-filled rash, rash

Symptoms that always occur with skin abscess: rash with bumps or blisters

Urgency: Primary care doctor

Pimple

Pimples are also called comedones, spots, blemishes, or "zits." Medically, they are small skin eruptions filled with oil, dead skin cells, and bacteria.

Pimples often first start appearing at puberty, when hormones increase the production of oil in the skin and sometimes clog the pores.

Most susceptible are teenagers from about ages 13 to 17.

Symptoms include blocked pores that may appear flat and black on the surface, because the oil darkens when exposed to the air; blocked pores that appear white on the surface because they have closed over with dead skin cells; or swollen, yellow-white, pus-filled blisters surrounded by reddened skin.

Outbreaks of pimples on the skin can interfere with quality of life, making the person self-conscious about their appearance and causing pain and discomfort in the skin. A medical provider can help to manage the condition, sometimes through referral to a dermatologist.

Diagnosis is made through physical examination.

Treatment involves improving diet; keeping the skin, hair, washcloths, and towels very clean; and using over-the-counter acne remedies.

Rarity: Common

Top Symptoms: pink or red facial bump, small facial lump, painful facial bump, marble sized facial lump

Symptoms that always occur with pimple: pink or red facial bump

Urgency: Self-treatment

Molluscum contagiosum

Molluscum contagiosum, also called "water warts," is a common, benign, viral skin infection. It causes a rash of bumps that may appear anywhere on the body.

The virus spreads through direct contact with the bumps, including sexual contact. It also spreads through touching any object that an infected person has handled, such as clothing, towels, and toys.

Most susceptible are children under age 10. Other risk factors include dermatitis causing breaks in the skin; a weakened immune system; and living in warm, humid regions under crowded conditions.

Symptoms include a rash of small, pale bumps with a pit in the center. The rash is usually painless but may become reddened, itchy, and sore.

Diagnosis is made through physical examination.

In some cases, treatment is not needed and the condition will clear on its own. However, if the bumps are unsightly or are present in the genital area, lesions can be removed through minor surgical procedures or treated with oral medication or topical agents.

Rarity: Common

Top Symptoms: rash with bumps or blisters, leg skin changes, skin changes on arm, head or neck skin changes, genital skin changes

Symptoms that never occur with molluscum contagiosum: fever, headache

Urgency: Phone call or in-person visit

Lipoma

Lipoma is a word that translates as "fatty tumor," but a lipoma is not cancer. It is simply a growth of fat between the muscle layer and the skin above it.

The exact cause is not known. The condition does run in families and is associated with other unusual syndromes such as adiposis dolorosa, which is similar. Lipomas most often appear after age 40.

Symptoms include a soft, easily moveable lump beneath the skin, about two inches across. A lipoma is painless unless its growth is irritating the nerves around it. They are most often found on the back, neck, and abdomen, and sometimes the arms and upper legs.

It is a good idea to have any new or unusual growth checked by a medical provider, just to make certain it is benign.

Diagnosis is made through physical examination, biopsy, and imaging such as ultrasound or CT scan.

Most of the time, treatment is not necessary unless the lipoma is unsightly or is interfering with other structures. It can be removed through surgery or liposuction.

Rarity: Uncommon

Top Symptoms: skin-colored groin bump, marble sized groin lump, small groin lump

Symptoms that always occur with lipoma: skin-colored groin bump

Urgency: Wait and watch

Dermatofibroma

A dermatofibroma is a fairly common skin growth that usually appears on the lower legs, but may appear anywhere on the body. These mole-like growths are benign (noncancerous.)

The cause is not known, though a dermatofibroma may appear after a minor injury. The growths are not contagious.

Dermatofibromas are most common in adults and are rarely found in children.

Symptoms include a hard, raised growth that is red, pink, or brown and less than half an inch across. They are usually painless but may be tender or itchy, and may appear alone or in groups.

Any new growth on the skin should be seen by a medical provider, especially if the growth is very dark in color or changes its shape or appearance quickly.

Diagnosis is made through physical examination and sometimes biopsy.

A dermatofibroma does not require treatment unless it is interfering with clothing or is unsightly. They can be surgically removed, though this will leave a scar and the growth may eventually return.

Boil (furuncle)

A furuncle, also called a boil, is infection of a hair follicle. The infection forms under the skin at the root of the hair and may occur anywhere on the body.

The infection is caused by bacteria, most often Staphylococcus aureus or "staph." Irritation caused by clothes or anything else rubbing the skin can cause the skin to break down and allow bacteria to enter.

Staph bacteria are found everywhere. Frequent and thorough handwashing, and otherwise maintaining cleanliness, will help to prevent its spread.

Most susceptible are those with a weakened immune system; diabetes; and other skin infections.

Symptoms include a single bump under the skin that is swollen, painful, and red, and contains pus.

It is important to treat the boil, since infection can spread into the bloodstream and travel throughout the body.

Diagnosis is made through physical examination and sometimes fluid sample from the boil.

Treatment may involve incision and drainage of the infection, followed by creams to apply to the site of the boil and/or a course of antibiotic medicine.

Rarity: Uncommon

Top Symptoms: pink or red facial bump, small facial lump, painful facial bump, marble sized facial lump, constant skin changes

Symptoms that always occur with boil (furuncle): pink or red facial bump

Symptoms that never occur with boil (furuncle): fever

Urgency: Self-treatment

Basal cell carcinoma

Basal cell carcinoma (BCC) is the most common kind of skin cancer. It can develop almost anywhere on the body. It appears as abnormal spots or bumps on the skin. These bumps are often pink, red, or skin-colored and sometimes have a shiny surface. The main risk factor for developing this condition is prolonged exposure to ultraviolet (UV) radiation. Sun exposure and tanning beds are both sources of UV radiation. People with a history of sunburns, previous skin cancer, and a weakened immune system are at higher risk for this condition.

Most cases of BCC can be easily treated because they grow slowly. Though if not treated, it can spread inside the body. Your provider will do a skin exam and possibly skin sample test, known as a biopsy. Treatment will depend on where the cancer is, its size, and your medical history. Some treatment options include cutting out the bump, freezing it, or using medicated skin cream.

Rarity: Uncommon

Top Symptoms: facial skin changes, pink or red facial bump, small facial lump, painless facial bump, growing facial lump

Urgency: Primary care doctor

Questions your doctor may ask about bump on the bicep or tricep

  • What color is the bump?
  • Any fever today or during the last week?
  • Do you have a rash?
  • Do you feel pain when you touch the bump?

Self-diagnose with our free Buoy Assistant if you answer yes on any of these questions.

Bump on the bicep or tricep symptom checker statistics

People who have experienced bump on the bicep or tricep have also experienced:

  • 4% Pain In The Upper Arm
  • 4% Forearm Pain
  • 3% Upper Arm Redness

People who have experienced bump on the bicep or tricep were most often matched with:

  • 100% Pimple

People who have experienced bump on the bicep or tricep had symptoms persist for:

  • 32% Over a month
  • 31% Less than a week
  • 17% Less than a day

Source: Aggregated and anonymized results from Buoy Assistant.

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