It could be due to dryness of the skin, but the cause has to be found . Sometimes hypothyroidism can cause dry skin so you have to be evaluated. You should consult a dermatologist because by looking at the type of rashes you are developing we will get to know the cause for it and then treat you accordingly. Insect bites can cause rash, any infection can cause rash, any drugs you had been taking can cause rash.
Next Steps
better to consult a dermatologist
Health Tips
use milder soap, use good moisturizers, control pests, find out the cause for rash and try to avoid it