This question has arisen several times both on the forum and on HU so I thought I would 'blog' my thoughts so they can be more easily found in the future!
It’s a tough call but a necessary one. Another juggling act that is included in the RA circus. Do we allow ourselves the pleasure of being doused in the sun’s rays? Do we accept the lashings of Factor 50 sun cream at regular intervals? I must admit to feeling so much better having had a session in the sun. At what price though?
Certain RA drugs are known to cause photosensitivity. Not just Methotrexate but also Sulfasalasine, Hydroxychloroquine and Myocrisin (Gold); there may be others too. In a phototoxic reaction, drug molecules absorb the energy of a specific UV wavelength, which cause the molecules to undergo a chemical change and emit energy that damages the surrounding tissues. It usually display as redness or sunburn.
The skin is basically being burned (more than it would ordinarily be in the sun) because of the action of the molecules. You are then relying on the body's healing system to effect adequate repairs. Our immuno-suppressant drugs do not assist the healing process, as we know, and is the reason why they have to be stopped during illness and surgery. I'm not sure how this may affect things long term, but I suspect, and these are only my own thoughts so please don't go jumping around in fear, that any damage/lesions caused to the skin by sun exposure may lead to longer term problems.
Many years ago I was on methotrexate and high dose steroids. I went abroad several times in one year (felt so much better in the sun) but I developed a skin problem as a result of too long on my sunbed, reading and dozing (which was doing wonders for the RA but obviously not my skin!)! No-one seemed to know whether it was due to 'thin skin' from the steroids or the effect of burning due to MTX or even a combination. The skin just peeled away (mainly on my hands and arms) leaving patches of weeping open sores. Many antibiotics, many months later they healed but left small white scars all over the place! These bits now have no pigmentation and burn very easily.
The recommendations are that you use a light barrier cream at all times and high Factor sun cream when in the sun. Avoid strong sunlight particularly between 11am and 3pm and at all times use the shade to benefit from the warmth. I still go out in the sun but smothered in cream and re-applied very regularly!
Guess you take your chance!