Is Sunlight Causing Hair Loss?

3 months after the onset of summer my hair starts to shed/regrowth more, it reaches a peak then goes back to normal. Do you know if this is because we are subjected to longer daylight in summer or is it that we absorb more sunlight. Its only more noticeable to me since I lost hair due to iron deficiency.

Humans have asynchronous hair growth, which means we shed and regrow hair uniformly as a general rule, so sunlight should not cause hair loss. Clearly, when you added hair loss due to iron deficiency (and what else?), there are other factors that make my opinion inadequate in giving you a knowledgeable answer. For example, many people with iron deficiency have anemia as well, which also leads to hair loss.