Hi,
Thanks for writing to us.
You seem to be developing polymorphous light eruption or in simple terms allergy to sun.
So the first and foremost step should be sun protection. For the same use a sunscreen with SPf at least 30 daily. Use gloves and cotton clothe to cover face and arms. Apply steroid cream over itchy lesions of your arm. If similar lesion develop over face, you may use steroid cream like mometasone or fluticasone over face too. The lesions that have become dark or brown can be treated with regular application of Kojic acid and vita,in chased cream like kojivit.
Hope that helped.

Hi, thanks for posting your query to us.

You seem to have increased sensitivity to sun light ( means you are allergic to sunlight). The changes that you have described when you go out in sun that is dryness , redness, itching, are due to the effect of UVA and UVB rays on the exposed parts of the skin. This is called polymorphic light eruptions.

To treat the same:

First thing is to avoid sun exposure especially from 10 am to 3pm when sun rays are most harmful.

Apply a sunscreen lotion in the morning , repeat it every 3-4 hours during the day time. For a sunscreen to be effective it should be applied half an hour before you go out.

On the red and dry spots you may apply a steriod cream by doctor's advice.
Don't scratch the itchy spots, as they may worsen the problem and leave brown spots which lighten very slowly even after treatment.

You may contact a dermatologist for most suitable sunscreen according to your skin type and the steroid cream.

I have tried to write in a very simple way for you, I hope you understood it but still if you have any doubt, please let me know.