Young people often suffer from a skin condition (spots) known as acme. This is a bacterial infection of the small glands in the skin which are fatty.
The usual treatment is to wash the skin with soap and water, however this is not always sufficient. I've found that an antiseptic cream applied all over the effected area will fix the condition. To be successful the cream needs to be applied every day twice a day until the eruptions disappear and then once or twice a week until the sufferer is about 25 years old.
Another Condition, a persistent skin rash, is sometimes caused by a fungal infection of the skin (at least it is manifest on the skin but may be throughout the body). This will be treatable by a fungicide. If it is only superficial then a skin cream for fungal infections may be effective. If it is general, then a course of systematic antibiotics for the infection is required.
Some of these skin conditions are extremely contagious and will spread rapidly through normal contact, in others, although they are infections do to spread easily by contact but only through cuts.
I've successfully used "Boots antiseptic cream" for acme and "Daktarin Gold" for a superficial fungal infection, respectively.
Disclaimer
I am not a doctor, nor do I have any medical qualifications, the treatments I describe were recommended for me by my general practitioner.