You say he has a rash and then an infection. A rash is often an allergic response, an infection is a totally different issue and would not be treated the same way. So does be have a rash - red, itchy, slight swelling or an infection, red, painful, more swelling (usually), feels hot, there may be pus ? An infection would be treated internally and topically if it was mild with antibacterials (essential oil of lavender, EO of tea tree, Myrrh tincture, Goldenseal tincture Usnea tincture, etc). More severe infections (red streaks down the finger or hand, feels hot and is painful, they may also have a fever) need antibiotics. A rash is usually treated topically, although some antiinflammatory immune-regulatory herbs (Turmeric, Sarsaparilla, Gotu Kola) may be useful internally in some cases.