Very minor. Generally, laser hair growth helmets, laser caps, laser combs, and similar devices that deliver light energy to the scalp are considered safe, with studies showing no major side effects. But that’s not to say that some minor issues can’t occur — some might still experience slight scalp irritation, sensitivity, or occasional headaches.Very minor. Generally, laser hair growth helmets, laser caps, laser combs, and similar devices that deliver light energy to the scalp are considered safe, with studies showing no major side effects. But that’s not to say that some minor issues can’t occur — some might still experience slight scalp irritation, sensitivity, or occasional headaches.