Dermatitis, or inflammation in the skin can cause this pattern.
Eczema (atopic dermatitis) can do this, and the rash associated with gluten allergy (celiac sprue) called dermatitis herpetiformis can also do this. Hives can present similarly as well. Erythema multiforme is rare, but can appear this way and eventually makes little "target" lesions. A dermatologist should be able to diagnose you.
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