Exposure to ultraviolet light (particularly in the B spectrum) from sunbathing can exacerbate the disease in SLE patients, and approximately 70% of SLE patients have disease activity as a result of UV exposure.DNA exposure to UV increases thymine dimers, which are more immunogenic. Exposure of keratinized cells to UV light induces apoptosis, and during apoptosis its own molecules can be exposed to the immune system and become immunogenic. UV light can cause cell damage to produce heat shock proteins, which can be involved in the activation of autoreactive T cells. Some epidemiological studies have found a possible protective effect of UV exposure in multiple sclerosis and rheumatoid arthritis, but UV exposure has been found to increase the risk of autoimmune disease in genetically susceptible animal studies. Some studies have suggested that hair dyes and perms may increase the risk of SLE in women, but this has not been recognized.