Itchy arms, ankles, forehead, scalp from sun exposure

I get an itch, not so much of a rash, on all the body parts that are exposed to the sun, even on cloudy days, everytime I go out. It is most intense in the summer months. It started about 20 years ago (I am now in my early forties) with just the forearms and back of hands and fingers. I did not use anything initially, it just went away withing an hour or so of being inside. I saw a doctor a few times but no one has been able to offer a permanent solution, even something that reduces the impact. Over the years I have found that putting sunscreen on before I go out greatly reduced the impact of sun exposure. For years I simply used Coppertone Sport (applied only to the arms) and that seems to have worked (the highest SPF available at a given time). For the last 4-5 years, I get it even from a few seconds of sun exposure, and it has spread to other exposed body parts - forehead, face, top of ears, scalp (perhaps because of thinning hair), neck - front and back, top of feet and toes, upper arm, and ankles (when I wear skirts or capris). I still use sunscreen, now on all my exposed body parts, except scalp of course, which I try to cover with a hat. Now I use Aveeno Active Naturals, for the last two years, thinking it may have less harmful chemicals (I have been trying to eliminate chemicals and processed foods from my home and life, both inside and outside - in things I can control).

Lately, even despite applying sunscreen, I get an itch on my ankles and the top of feet, at night. If I scratch it too much, it gets worse. I apply all kinds of lotion and aloe vera containing gels before going to bed but that only provides temporary relief. It is usually gone by the morning.

I am from India, and I was there this summer for three months. It was pretty hot there. I went out in the sun multiple times, often in over 100 degree temperatures, and nothing happened, even when I forgot to apply sunscreen. I wonder if it is the air pollution blocking the UV rays?

Does anyone know what my condition is called? I am looking for a name and explanation from someone who has seen it before. Most dermatologists and doctors, I am sorry to say, just keep guessing and experimenting so please don't answer this unless you really understand my condition and know what you are talking about.

thanks