Hi and welcome to HCM
You may have developed a condition called
tinea versicolor, which is a mild
fungal infection caused by increase in the normal fungus present on the skin. It may be aggravated by sweating or due to recent illness which might have reduced your immunity, dandruff.etc. it does tend to itch and turn reddish on sun exposure.
To treat this you will have to take a single dose of antifungal like
fluconazole 400mg followed by long term application of anti fungal cream. If it is over a large area antifungal liquid suspension maybe required before showering.
ketoconazole soap may be used for bath. It takes close to a month for infection to be treated, and skin color takes longer to return to normal. This is the most probable cause and will need to be confirmed by a dermatologist. If persistent, skin tests can be done to check.
Other possibilities to keep in mind are sun allergies, early stages of vitiligo or pigment loss, or
hypopigmentation as a result of some skin reaction. these will need to be ruled out after consultation.
You can start on the treatment as advised. Keep dry and clean. Antihistamines can be used in case of
severe itching.
Consult a dermatologist if you see no improvement.
Hope this helps.