Based on the information there are two possible causes which are as follows
1) Fungal infection
(commonly known as ring worm infection
) - most probable cause
2) Allergic reaction
)- second most probable cause
Please contact PHYSICIAN ,
Reason is its hard to come to conclusion just from the description and a visual conformation / touch may be needed and may need some diagnostic test to pin point the cause.
Here is mostly all physician tend to do
1) physical examination
2) visual inspection and touch to feel the changes
3) may need a KOH test in case of fungus
4) may need to do blood test
, or allergen test for finding out the cause
a) Prescribe the antifungal cream for the ringworm in case of fungal infection.
b) In case of allergic reaction will ask you to stay away of the allergen and may prescribe you antiallergenic drug