Hello lionOO,
I know you already have the rash but I thought this info might be of use to you. Look into PLE - polymorphic light eruption. Most people confuse this with prickly heat but it is very different.
A short overview for you :-
Polymorphic light eruption (PLE), otherwise termed polymorphous light eruption (PMLE), is a skin complaint caused by sunlight.
Typically, those affected by it will have been exposed to the sun for two to three days while on holiday, although the complaint does occur between the spring and autumn months in the UK, and sometimes as little as 15 minutes exposure to sunshine can induce the condition. It can even be brought on by sunlight penetrating through a window or thin clothing.
A delayed-onset, spotty, itchy eruption appears on the skin, and may take between 5 to 10 days to clear.
The rash usually consists of small red spots or blisters and can appear on any part of the body that has been exposed to sunshine, although commonly the face and the backs of the hands will be spared. It tends to heal without scarring.
It is not the same as prickly heat. This occurs during warm weather, generally affects the trunk (ie, not the head, neck or limbs) and is related to overheating, particularly in areas where there is friction due to clothing.
There is quite a bit more info on it, but I think this will give you an idea so that you can be aware of how it can happen and how to treat it.
Hope this is of help to you.
goldenwings