This question is one of the most frequently asked. I have already mentioned that our skin is one of the main organs through which toxic admixtures go out. One must not "smear" different appearances of skin rash, no matter how they look like - dandruff, tinea, herpes, blackheads, diathesis. The best variant is when after using an ointment there will be more appearances of skin rash. If the constitution is weak, there will not be appearances of skin rash, but one is sure to suffer from inner diseases. It is well-known in the traditional medicine that each organ has its representative zone on the skin. In beauty parlours or dermatologists' consulting rooms inner organs are treated in the case of skin problems in different zones. But the homeopathic point of view differs. Do not treat an inner organ, for example your stomach, if there are appearances of skin rash. Any medicine is a toxic product and additional toxins are surely will not help to clean your skin. Never put anything into the water for washing, do not use any ointments - clear water, steam, good (not antibacterial) soap - this is the best way to get rid of toxins through the skin. If your skin is clear, you can use make-up, but if there are any problems just do not disturb them. If appearances of skin rash stay for a long time - take your constitutional remedy.
I would like to draw your special attention to the suppression of the functioning of sweat glands. If the sweat has become excessive or fetid - you should help your organism to get rid of what it wants. It is up to you - to choose sports or a sweating-room, but do not use antiperspirants (by the way the suppression of sweat glands is one of the main causes of the breast cancer).
It is very important to keep to the rules in the teenage period. This period, as well as pregnancy, is the time when the nature gives a chance to an organism to recover, a chance to clear itself: appearances of skin rash, blackheads, dandruff, sweat, genital secretion appear. Earlier, when we did not have so many cosmetics, we used to say "he will grow up" and really we observed that a child with some chronic ailment recovered at the period of its sexual puberty. We do not see such cases now days.