How do we differentiate between the various types of skin rashes like atopic dermatitis, heat rash and jock itch? (photo)

Sorry to hear that your skin rashes are breaking out all over. Sandfly or insect bite reaction is due to a hypersensitivity response of your body to the insect bites. In susceptible individuals, the body mounts a hypersensitive or ‘allergic’ response to the foreign protein deposited in the skin from the bite. The reaction can persist for weeks to months after the initial insect bite. People with atopy (ie asthma, eczema or allergic rhinitis/sinus) may be more susceptible to insect bite reactions.

Thanks for the very clear history and photographs. The red rash looks like a bruise and this is likely to be due to excessive pressure over the area, aggravated by the compression from the stripes which squeezes the enclosed areas. This will typically take 1 to 2 weeks to resolve. Blood tests are usually done to rule out underlying conditions like low platelets which may lead to increased susceptibilty to bleeding. I assume these tests were done and were normal. I would suggest wearing leotards without this stripe pattern so that there will not be added pressure to the skin.