Rapamycin photosensitivity?

My second week taking 2mg weekly. Noticed a little more energy, but so far so good. One unusual thing I noticed is that when I’ve been out in direct sunlight, the sun feels like it is literally burning my skin like a laser. I was shocked at how hot it felt. It felt dangerously hot, like touching a stove. Can’t be sure it’s related to the rapamycin, but has anyone else experienced this?

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I’ve not heard of anything like what you are describing. Have you had any other changes in your supplements or medications?

Ahhh… here is a reference:

This medicine may make your skin more sensitive to sunlight and can increase your risk of having skin cancer. Use a sunscreen when you are outdoors and avoid sunlamps and tanning beds.

From here:

I put on sunscreen everyday anyway, so no change of behavior for me - but other people should be aware of this.

The only other research I can find related to this topic is this:



Thank you for the info, I’ll definitely be more conscious about the sunscreen. Probably a good thing to do either way really.

It’s interesting to see that rapamycin can also be protective in certain situations.

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Increased susceptibility for people on immunosuppressants.


Sun exposure is weirdly contentious topic these days, with some saying sun avoidance is important and some saying sun exposure is essential for vitamin D production and hormone health. I think at minimum, you want to make sure to be a little cautious and not overdo it.


Check with a dermatologist. Nobody here can give you medical advice. Could be anything.

When you ask questions about side effects to your dermatologist, it’s best to have the entire routine down and exact details, as well as conditions (time of day, weather conditions, UV index) on the first and second time (and when exactly you took what). For example, just peeling a grapefruit can cause phytophotodermatitis. It could be anything.

Just reading this - my question would be it seems weird you didn’t have any reaction the first time?

From my understanding, sirolimus-induced photosensitivity, if it exists, is very rare. If sirolimus at low weekly dose is really causing immunosuppression, it may be associated with UV-induced skin tumors, but my understanding is it is an immunomodulator/immunostimulatory (depends on situations) and anti-inflammatory. There are even trials showing sirolimus or derivatives as a treatment/prevention for skin cancers.

And it’s pretty common sense to avoid all UV sources always according to the American Academy of Dermatology (unless your physician said so), but at low doses once per week, I am doubtful about these labels intended for kidney transplant patients.

Not medical advice!