Someone Ill with a Non-Life-Threatening Illness
One who is ill (meaning that he is actually bedridden and the like, even if the illness is not life-threatening) is exempt from fasting on Tisha Be’av. When in doubt about one’s status, one should consult a prominent halachic authority. (Aches and pains, such as the common headache and the like, are not grounds to exempt one from fasting on Tisha Be’av.)
The Elderly
An elderly person who is weakened by fasting is considered “ill” for all intents and purposes and is exempt from fasting on Tisha Be’av. Even if he has no internal illness, he must eat on Tisha Be’av. However, if the elderly individual is not actually ill and has merely been advised by doctors to eat on Tisha Be’av lest the fast weaken him and cause him to fall ill, he should eat or drink small amounts and in spaced out intervals of ten minutes, similar to the law on Yom Kippur (Chazon Ovadia-Arba Ta’aniyot, page 279).
A Woman Who Has Given Birth
Regarding a woman who has given birth within the past seven days, all opinions agree that she is exempt from fasting on Tisha Be’av. However, if she has given birth more than seven days before Tisha Be’av but is still within thirty days of giving birth, several Poskim are of the opinion that she must be stringent and fast on Tisha Be’av. Nevertheless, Maran Rabbeinu Ovadia Yosef zt”l rules that as long as the woman is within thirty days of giving birth, she is exempt from fasting.
The same applies to a woman who, G-d-forbid, miscarries following at least forty days of pregnancy (meaning that she miscarried a fetus who was in the womb for forty days or more; these forty days are counted from the actual conception, not the way the doctors calculate beginning from two weeks later) in that she is exempt from fasting on Tisha Be’av as long as she is still within thirty days of the miscarriage.
Pregnant and Nursing Women
Although pregnant and nursing women are exempt from all other public fasts (besides for Yom Kippur), they are nevertheless obligated to fast on Tisha Be’av (besides for a year when Tisha Be’av coincides with Shabbat which we shall not discuss at the moment). Nevertheless, if they are feeling ill (due to vomiting, feeling faint, and the like), they share the law as any other ill individual, even with a non-life-threatening illness, and are exempt from the fast.
Important Note: Anyone who is exempt from fasting on Tisha Be’av due to illness, such as, an ill individual, a woman who has given birth within thirty days, or a pregnant or nursing woman who feels ill, may eat and drink regularly and is not required to eat small amounts in spaced out intervals as is the law regarding someone ill on Yom Kippur (Chazon Ovadia-Arba Ta’aniyot, page 288).
Children
Children, meaning a boy who has not reached thirteen years of age and a girl who has not reached twelve years of age, are completely exempt from fasting on Tisha Be’av. The reason why children are exempt from participating in this fast is because children are exempt from all of the laws of mourning in general. Indeed, if G-d-forbid a child loses a parent, he need not mourn at all, for the Mitzvah of educating children does not apply here (besides for the law of rending one’s garment which applies to children as well). Any boy who has not reached the age of thirteen or girl who has not reached the age of twelve is completely exempt from the fast and they need not even fast for several hours.
