Red bumps, itching on skin when body gets warm?

Reasons: 1. Allergy probably. Take "Actifaed" it is over the counter medicine for allergy if it goes away it is allergic reaction to heat(reason for it could be climatic or food, air born allergens, any thing else). Allergy shots after testing may be a good way to build immunity. 2. Prickly Heat, Johnson and Johnson had "Prickly Heat Powder" in blue container and "Baby Powder" in orange- yellowish container use that after bathing, or when this happens. Go for a dip in the ocean(salt water is batter beside salt it has other good stuff that may be helping) or river or any large body of water(55 F will do the trick),do not go if it is not allowed for health reason(in that case most well known swimming area will have hazard sines posted). Stay in an air condition office or area. Keep a bag handy fill it up with ice or cold water and apply it to the area. 3. If female "Hot and cold flashes", see a doctor and get it treated with combination treatment(oestrogen- progesterone). Rare but some man may get this too. Key here is adjusting the body chemistry by taking Hormonal treatments, must get blood work done. 4. See a doctor (dermatologist when this happens, or take a picture to show it to a dermatologist).

heat rash. lots of people get this. Just chill the areas with ice whenever you can

I've never get that but I observe my friend from kazakstan, where has no sea and dry cold, she get that kind of itchy after the sun also she couldn't eat seafood throught the geans is like a mountian people and her family has never intermarry to the city people or the other nation.