I was diagnosed with sarcoidosis in 2006, and in my visits of sarcoidosis sites, facebook and twitter, there is always one common complaint from people with the disease, and that is “I get so angry when people tell me 'But you don't look sick'”. Well I found that there is a very easy way to get around that.
It's simple. Don't go around telling everybody you come across that you have a disease, because as harsh as it may sound, 75% of the people you tell really don't give a damn, 15% don't want to hear about it because they are afraid of their own mortality, and such things only bring up those thoughts, 9% just have no idea what to say or do and feel helpless, and only the final 1% are those that really do care.
Also, there is a great thing about the universe, it will always try to please you, so going around announcing to the world “I am sick”, and you are telling the universe, the world and yourself that you are sick, and the universe, the world and your body will do all they can to oblige. Whenever anyone asks me how I am doing, no matter how shitty I feel, I always say “I'm fine, thanks”, because by telling myself I am fine, my body will try to respond as such.
Give it try. Instead of compaining that people dont understand that you are sick, try not giving people the opportunity to question your validity. Just say nothing about your illness, and no one will have any reason to make a snide remark.