Someone who gets sick after a taanis (in a way that if he would feel this way on the taanis itself he would be patur from fasting) does such a person have any heter lichatchila to not fast?
Answer:
There is no obligation to fast, but he should eat less than a shiur at a time.
Sources:
Halichos Shlomo, Taanios Chap. 13, no. 5.
