Nettle Rash on Face, Neck and arms...

My 4 year old son (with many other health problems besides) started to get horrible rashes all over his face about 2 months ago (mid February). We assumed it had been a new medication that he had been taking so we stopped the medication and the rash appeared to go away, only to return 3 days later.

We took him to the ER where he was diagnosed with 5th Disease. He still has the rash (2 months later), but the past few days it has gone from a small nuisance to a huge problem. His face is covered in small clear bumps and large, blotchy, red, raised patches that look like blistered burns.. same with his neck and his arms are red with little clear bumps.

Although I haven't had much luck with getting 2 and 2 to make 4.. I am assuming that he has a sun allergy.. perhaps Solar Uticaria or Polymorphous light eruption (PMLE).. because the rash started to become worse when we started going outside for prolonged periods when the weather started to get better.. and goes away (mostly) when we stay inside for a few days.

Is there anything that I can use to make his rash less itcy? It seems like I've tried everything. Last night we resorted to Benadryl, which we gave him at 5pm and by 9:30.. still hadn't done anything. Any suggestions?? We have a dermatologist appointment, but not until May 17th, and my son can't wait another 3 weeks before we do something about the itching.

Thanks in advance. Tweet