Acne

Acne begins in the oil gland that sits at the base of a hair follicle. Hormonal signals make the gland larger and more productive, the cells lining the follicle shed more stickily, and the opening blocks.

Bacteria that live on everyone's skin multiply in that blocked, oily space, and the immune system reacts to them. How deep in the follicle the blockage sits, and how strongly your skin responds, is what separates a small blocked pore from a deep tender swelling that lasts weeks.

It runs in families, it tracks with hormones, and it is common from the early teens into the twenties and thirties, particularly in women. Diet and washing matter far less than most people expect, and scrubbing inflamed skin harder makes it angrier.

Your dermatologist makes the diagnosis by looking at your skin in good light, across the whole face and also over the chest, shoulders and upper back, where it is easy to overlook. They are establishing which kind of lesion dominates, how deep the inflammation reaches, and whether the skin has already been damaged, because those three things set how firmly it needs to be treated.

They will ask how long it has been going on, what you have already used and for how many weeks, what goes on your skin each day, and what medicines you take, since several bring acne on.

In a woman whose acne started late or resists treatment, they will ask about your cycles and your weight, and may arrange blood tests when the pattern points to a hormonal cause.

Acne treatment works on a slow clock. Skin often looks slightly worse for the first two to four weeks before it turns, six to eight weeks is the earliest point at which any treatment can be judged fairly, and three months is a fairer one. Stopping at three weeks is the commonest reason a treatment that would have worked gets written off.

In-clinic sessions are given as a course spaced two to four weeks apart. Each one leaves the skin pink and sensitive for a day or two, so plan them around anything important in your calendar. No time off work is needed.

The marks left behind fade on a much longer clock than the spots. Brown marks settle over three to six months provided you use sunscreen daily, and a dent in the skin does not fill in on its own and is dealt with separately once the active spots are quiet.