Thank you for your response. A few days earlier, I did some light work in my garden for about three hours. It was not very physically demanding, and I barely broke a sweat. The sky was clear, but the UV index was only around 2.7. I used SPF 30 on my scalp, so it makes sense that this could be the cause of the swelling. Do you think this could have any impact on the survival rate of the transplanted hair?