Red or Sore Lump on Breast, Armpit, Skin, Back or Penis: Causes, Symptoms, Pictures

Red or sore lumps on different parts of the body are usually painful. This is because they are common signs of infections, diseases, and health conditions. All the same, such a lump can be caused merely by skin irritation.

Most red and sore lumps will resolve even without treatment. This should not be taken as grounds to dismiss your doctor’s advice or the need for medical diagnosis. Although it is very unlikely that the most dangerous end result of a lump, cancer, will start in form of a red sore lump, there are other diseases which are just as dangerous.

This article discusses the appearance of a red or sore lump on the breast, under the armpit, on skin, on the back and on the penis. See your doctor for diagnosis confirmation.

Red lump on breast causes

Yeast infection

A yeast infection is characterized by a rapidly spreading rash and red, itchy pimples on the nipple. It requires treatment with anti-fungal medications.

Acne and folliculitis

It is common to develop acne on the breasts, especially for women about 2 weeks before menstruation. Irritated acne forms red bumps which can be itchy and painful. Inflamed acne due to bacterial infection or irritation is known as folliculitis. It causes sore and red lumps on the breast around hair follicles.

Subareolar abscess

A red, sore lump on the nipple due to breast infection such as mastitis is known as a subareolar abscess. Accumulation of pus makes the lump tender and painful. It is common in breastfeeding women.


Breast cancer lumps are usually painless, hard and not sore. In some cases, skin redness accompanied by nipple retraction and discharge may occur. See your doctor if a lump in your breast persists for more than 2 weeks.

Red lump under armpit causes

A red lump under the armpit can be caused by any of the following:


Acne can develop on any part of the skin. On the armpit, sweat may repeatedly irritate the acne, resulting in a sore, red pimple. If the irritation is severe or infected, folliculitis will develop. Folliculitis is characterized by inflammation and swelling of hair follicles.


Boils are very common in the armpit. They originate in hair follicles or oil glands. Initially, a red bump will appear. Due to presence of bacteria, pus will accumulate and result in a sore bump with a white tip. Within 5 days, the tip may burst open or crust over. Boils are usually painful, tender and warm. Large boils form abscesses.


Cysts are slow-growing, fluid-filled sacs that form bumps under the skin. Some cysts are hard and firm while others feel soft and slightly movable. Generally, they are not painful. Pain may develop due to irritation or formation of large cysts.

Swollen lymph nodes

The armpit is a common location to find swollen lymph nodes. This can be caused by an infection such as an abscess or diseases such as lupus, mumps or cancer. See your doctor if you can’t seem to find the reason as to why your lymph nodes are swollen. Also get immediate medical attention if you also notice a lump in esophagus on either side of neck, groin area and behind ears. Multiple swollen lymph nodes indicate serious infections and diseases.

Red lump on skin causes and symptoms

The skin is the largest organ in the body. Quite a number of factors and conditions can be responsible for a red lump on skin. They include:

Damaged blood vessels

Capillaries are quite delicate and due to their proximity to upper skin layers, they often sustain enough trauma to damage them. After damage, blood leaks under the skin. The blood may form a clot and result in a lump under the skin. For example, a lump on forehead under skin can develop after hitting yourself against a hard surface such as a wall. This is known as a hematoma. In mild cases, only a red spot will appear.


This is inflammation of hair follicles. It is mostly caused by bacteria and irritation. More than one hair follicle can be affected.

Keratosis pilaris

Common symptoms of keratosis pilaris include small red bumps and dry skin patches that mostly appear on the buttocks, thighs and arms. It is thought to be caused by skin dryness and worsens during dry weather conditions.


Pillar cysts and epidermoid cysts are common on skin, especially on neck and trunk. Since cysts form under the skin, most of them take the color of skin. Infected ones appear red and sore. Pressure or trauma may also make cysts painful. For example, a cystic lump on shoulder blade can become painful after repeatedly carrying heavy loads on your shoulder.


This is an autoimmune condition characterized by red scaly patches of inflamed skin. Psoriasis bumps form due to accumulation of dead skin layers. It mostly affects the knees and elbows and tends to be itchy due to skin dryness.

Cherry angiomas

Cherry angiomas are dilated blood vessels that appear as red lumps under the skin. They don’t cause any symptoms such as pain, itchiness or soreness. For this reason, they don’t require treatment.

Skin irritation

Allergens and irritants such as some beauty products, chemicals, acids, metals and some medications can result in a red lump on skin. In most cases, the skin around the lump will also redden or swell.

Sore red lump on back causes

A sore, red lump on the back can be caused by:


Papules and pustules are usually small, red bumps that originate in hair follicles. They can become infected or irritated to form sore and red bumps.


A sore red lump on the back can be an infected sebaceous cyst. Cysts are fluid-filled sacs that develop under the skin. Normally, they take the color of skin but can turn red and swollen if infected.


This is a bacterial infection that often occurs when you have a cut or cracked skin. It is characterized by a red sore lump that rapidly spreads.


Boils start as red sore lumps but quickly grow into white-tipped lumps. They mostly appear on the neck and armpit but can also develop on the back.


Scabies is not a disease but an infestation. Small mites invade the skin and form tunnels on the skin. The tunnels appear as red tiny lumps that are intolerably itchy. Scabies poorly responds to home treatments.

Red lump on penis symptoms and causes

A red lump on the penis can be a bit scary. Any of the following can be responsible:


Sexually transmitted diseases are common causes of red lumps, lesions or blisters on the penis. See your doctor if you have recently had unprotected sex. You find that quite a number of STDs can be responsible for such a lump.  For example, primary syphilis causes a single, painless, red lump above penis. Herpes, on the other hand, causes multiple red bumps in the genital region. Only your doctor can correctly identify the STD after diagnosis.

Sebaceous cysts

Sebaceous cysts are quite common on the penis shaft. They can become infected and form red bumps under the skin.

Pearly penile papules

These are the tiny red bumps located at the base of the penis head. They are very normal and totally harmless.


This is a harmless lump that develops due to accumulation of lymphatic fluid under the skin. It mostly develops after rough sex or masturbation. Lymphoceles do not require treatment.


Folliculitis can develop due to irritation when shaving or due to sweating. Presence of bacteria and fungi in the genital region can also encourage inflammation of hair follicles. Sweaty and hidden body areas are very prone to this condition. It is for this reason that a pea sized lump in anus can result from inflamed hair follicles.

Allergic reaction

Some soap brands or lubricants can irritate the penis, resulting in red irritated bumps.

When to see a doctor

The causes we have discussed here are only the most common ones. This means that a lump somewhere in your body might not be caused by any of them. Additionally, diseases such as measles and chicken pox have not been discussed. To stay on the safest side, see your doctor if a lump is intolerably painful, itchy or is causing swelling, pus formation, fever and swollen lymph nodes. Much the same can be said about a lump the cause of which you can’t seem to find.

You can learn a lot more on topics such as where is a testicular cancer lump located, signs of breast cancer and more online. There are many advantages of getting fully informed about your health. But, as it will repeatedly be mentioned, always talk with your doctor routinely.