It is common to observe that one armpit might appear to have more fat than the other. This reflects a broader biological reality: the human body is not perfectly symmetrical, and localized fat distribution can vary from one side to the other. This natural variation is influenced by several factors that contribute to how and where fat is stored.
Normal Body Asymmetry and Fat Storage
Human bodies are inherently asymmetrical; the left and right sides are not exact mirror images. This extends beyond external appearance to internal structures, where organs like the heart and liver are not centrally located. Minor differences in limb lengths, muscle development, or eye placement are common examples of this natural asymmetry.
Fat cells, or adipocytes, primarily store energy as triglycerides. Their distribution is influenced by genetics, hormones, and overall body composition. Genetic factors determine where fat is stored and mobilized, while hormones like insulin, estrogen, and testosterone regulate storage patterns. For example, estrogen promotes lower body fat, while testosterone and cortisol influence upper body and abdominal fat. This interplay contributes to natural variations in fat distribution, including differences between armpits.
Specific Reasons for Underarm Lumps
Several specific factors can contribute to the appearance of fat or lumps under one armpit, beyond general body asymmetry.
Accessory breast tissue, also known as polymastia or supernumerary breasts, is a common reason for a fatty-like lump in the armpit area. This tissue consists of mammary glands that develop outside the typical breast region, often along the “milk line” which extends from the armpit to the groin. It can become more noticeable and feel like a fatty lump, particularly with hormonal changes such as puberty, pregnancy, or menstruation, due to its responsiveness to these hormonal shifts.
Lipomas are another frequent cause of soft lumps under the skin. These are benign, non-cancerous growths made up of fat cells that accumulate in a capsule just beneath the skin. Lipomas are typically soft to the touch, movable when pressed, and usually do not cause pain. They can occur anywhere on the body where fat cells are present, including the armpit, and may vary in size.
Localized fat deposits can simply be an accumulation of subcutaneous fat in the armpit region. This can occur due to general weight gain, where the body stores excess energy in fat cells throughout various areas. Even with overall weight gain, natural body asymmetry or minor postural differences can lead to a slightly larger fat deposit on one side compared to the other, making it more prominent.
It is important to differentiate these fatty lumps from other types of underarm lumps, such as swollen lymph nodes. Lymph nodes are small, bean-shaped glands that are part of the immune system, located throughout the body, including the armpits. When the body is fighting an infection or inflammation, these nodes can swell and become noticeable. Swollen lymph nodes typically feel firmer than fatty lumps, may be tender or painful to the touch, and are not composed of fat tissue.
When to Seek Medical Advice
While many underarm lumps are benign, certain characteristics or accompanying symptoms should prompt a medical evaluation. A healthcare professional can provide an accurate diagnosis and ensure appropriate management.
Seek medical attention if an underarm lump:
- Rapidly grows or changes shape.
- Causes pain, tenderness, or redness.
- Feels hard, immobile, or irregularly shaped.
- Is accompanied by unexplained weight loss, fever, or fatigue.
- Shows skin changes like dimpling, unusual redness, or warmth.
- Produces nipple discharge (if accessory breast tissue).
- Is new or unusual, especially with a family history.
Managing Underarm Fat
For individuals whose underarm lump is determined to be primarily excess fat, several strategies can help manage its appearance. These approaches focus on overall body composition rather than spot reduction.
General weight management is the most effective way to reduce localized fat, including in the armpit area. This involves creating a calorie deficit through a balanced diet and regular physical activity. When the body uses stored fat for energy, fat cells throughout the body, including those in the armpits, will decrease in size.
Incorporating exercises that strengthen the chest and back muscles can improve the appearance of the underarm area. Activities like push-ups, chest presses, and rows build muscle tone in the surrounding regions, which can contribute to a firmer look and improved posture. Targeted exercises cannot directly reduce fat from a specific body part, as spot reduction of fat is not physiologically possible.
For persistent or bothersome fat deposits, such as large accessory breast tissue or localized fat that does not respond to diet and exercise, medical procedures are available. Options like liposuction, which surgically removes fat, or surgical excision for accessory breast tissue, can be considered. These procedures are typically a last resort and require consultation with a medical professional to determine suitability and discuss potential outcomes.