Painful underarm nodules are one of the manifestations of hidradenitis suppurativa, the condition that may alternatively be known as apocrine cysts or acne inversa. This is a chronic condition that will be present on a long term basis, once it has begun to develop.
Hidradenitis suppurativa affects the apocrine sweat glands and the hair follicles, primarily those located in the armpits and the groin area. Women seem to be more commonly affected than men, with approximately three times as many hidradenitis suppurativa patients being women as men. However, it is thought that the statistics are not a true representation of the total number of hidradenitis patients, so it could be a case of women seeking treatment more readily.
The condition begins with the appearance of nodules, or boils, in areas such as the armpit. This occurs when the apocrine sweat glands become blocked, and are no longer able to secrete fluids into the hair follicles. Instead, the substances build up in the narrow tubes leading from the sweat gland to the hair follicle, which causes inflammation and the appearance of the boils or underarm nodules. Sometimes, the boil will resolve and then reappear again in the same location, accompanied by additional boils in the surrounding area.
The boils will then start to fill with pus, at which point they are usually known as cysts or abscesses. The pus puts extra pressure on the nerves in the area, making hidradenitis suppurativa a painful condition. The pus may also start to leak out onto the skin as the abscesses increase in size, which means that the bacteria present on the surface of the skin can begin to act on the chemicals in the pus. When these chemicals are broken down by bacteria, a strong, foul odour is produced, which is another characteristic symptom of hidradenitis suppurativa.
As the severity of the condition increases, the abscesses will increase in size and they will become joined by a network of channels under the skin, known as sinus tracts. The sinus tracts will also be filled with pus, which can increase the pain considerably, and also lead to a large amount of leakage onto the skin.
When the abscesses and sinus tracts do eventually heal in places, which is likely to take a long time, patients will often be left with thick, unsightly scars. These can often be little better than the oozing wounds and swelling that was present before the healing.
Hidradenitis suppurativa will usually start to develop around puberty, which is when the apocrine sweat glands first become active. However, it can occur at any time after puberty, because of changes to the body that are caused by the sex hormones oestrogen (in females) and testosterone (in males).
The onset will usually have occurred by the age of 40, with most cases being diagnosed between the ages of 20 and 40, and the symptoms may settle down later in life. Women who are taking the oral contraceptive pill will often find that, because the levels of hormones are being regulated artificially, their symptoms will become less severe. It may be necessary to take the pill on a long term basis in order to keep the symptoms under control, which can lead to side effects. If you are concerned about the long term effects of taking the pill, then you should discuss it with your doctor. It is usually a better option than taking regular antibiotics, which can lead to antibiotic resistance, making the condition even harder to treat in the future.