Axilla

Anatomically, the boundaries of the axilla are:

The lower posterior boundary is called the posterior axillary fold and this is a compound structure consisting of the latissimus dorsi and teres major muscles.[8] It can descend after weight loss.[9]

The anterior boundary is called the anterior axillary fold and this is rounded in shape and formed by the lower border of the pectoralis major. Some sources also include the pectoralis minor.[8] It can elongate after weight loss.[9]

The contents of the axilla include the axillary vein and artery, as well as the brachial plexus, lymph nodes and fat. The axilla is the space between the side of the thorax and the upper arm.

• Axillary artery and its branches
• Axillary vein and its tributaries
• Infraclavicular part of the brachial plexus
• Long thoracic and intercostobrachial nerves
• Five groups of axillary lymph nodes and the associated lymphatics
• Axillary fat and areolar tissue in which the other contents are embedded

The underarm is a ticklish area, possibly due to the number of nerves it contains. Most people find this area to be particularly unpleasant when tickled.

Underarm hair usually grows in the underarms of both females and males, beginning in adolescence.

In some modern Western cultures, it is common for women to remove underarm hair.[11] Some view this practice as an aesthetic matter, while others view its removal for health-related concerns.[12] As underarm hair grows quickly, removal must be performed frequently, or stubble will appear in the axilla. In the Islamic tradition, underarm hair removal is a religious hygiene practice for both women and men. While most Muslims shave it, some pluck it, with products like wax, as it's more efficient to sustain longer periods without regrowing.

In the feminist movement, the hippie culture, and in the punk rock scene, some women retain their underarm hair for a variety of reasons, from subversion to egalitarianism to comfort.[13] Conversely but uncommonly, some men choose to remove their underarm hair for aesthetic reasons or to reduce friction in sports such as swimming.

Breast cancer typically spreads via lymphatic vessels to the lymph nodes found in the axilla.

Excessive perspiration without adequate air circulation can result in axillary intertrigo. Intertrigo is an inflammatory skin condition of skin folds exposed to friction or maceration in the presence of heat and moisture.[14] Intertrigo is worsened by infection, usually fungal (Candida yeast species), but also bacterial or viral; warm, wet underarms promote those growths.[15] The condition results in rash-like symptoms, pustules, or chronic itching or burning in the underarm.[14][16] Intertrigo (in any site) has no racial or sexual predilection.[14] Axillary intertrigo is common among those who work in hot environments where air circulation is restricted by necessary clothing or safety equipment.[17]