While receiving radiation therapy for breast cancer, at some point the skin over your chest or near the armpit slowly turns red. It can sting, and it burns as if you spent too long in the sun. The first time it happens, you may suddenly feel afraid, wondering "did I do something wrong?" But in fact this is a passing stage that almost everyone undergoing treatment goes through, differing only in degree. It happens because the radiation irritates not only the cancer cells but also the skin cells in that area, so it usually settles down within a few weeks after treatment ends.
Usually the reddish tint comes up about two to three weeks after starting treatment. At first it is just a faint redness, but as the sessions add up the skin becomes dry and itchy, and as it progresses further it may peel slightly or ooze a little. Areas where skin touches skin and sweat collects, such as the armpit or the fold under the breast, react especially sensitively. It is unsettling once the symptoms begin, but knowing in advance which spots are vulnerable makes you feel a little less anxious.
The key to care is simple. Reduce irritation, keep it moist, keep it cool. When washing, let lukewarm water flow gently instead of hot water, and use a mild, lightly scented soap, wiping softly with your hands. Rather than scrubbing hard with a towel, pat gently to lift off only the moisture. Choose a moisturizer free of fragrance and alcohol, but do not apply it right before the radiation session; apply it after treatment. As for clothing, wearing loose, soft cotton rather than something tight bothers the skin less.
Surprisingly, things people do without thinking irritate the skin even more. Placing a heat pack or ice pack directly on the treated area, applying patches or ointments on your own, shaving the armpit hair with a razor, saunas, hot baths, pool disinfectant, direct sunlight, and the like. If you scratch hard because it itches, that spot breaks down and recovery slows, so if you really feel itchy it is better to soothe it by lightly laying a cool, damp cloth to cool it down. When you are unsure what to apply, ask your medical team or nurse first before using anything. Hospitals often have a specific ointment they recommend.
What you eat also helps recovery a little. Not some grand restorative dish, but the key is not skipping meals that contain protein. Having even a little egg, tofu, fish, lean meat, or beans at every meal helps damaged skin fill back in with new tissue. Drink water more mindfully than usual, and it is even better to add vegetables or fruit rich in vitamin C. When you have no appetite, start with foods that go down easily and without burden, eating more often rather than in large amounts. Steadily setting an ordinary table is far more reassuring than loading up on particular supplements.
Most people get through it with this kind of care, but if oozing continues, the pain worsens, or you develop a fever, that is not something to endure alone. Do not hesitate to tell the hospital. What is written here is only general guidance, so the answer that fits your skin condition exactly is, in the end, best known by the medical team who is looking at you.