Acts Rendering The Fast Makrooh:
The following acts do not nullify the fast, but render it makrooh in the sense that they lessen the of the fast. Hence it is not advisable to indulge in any of the following acts when one is in the state fast:
(i) Chewing something or tasting it with the tongue without eating it.
(ii) Using tooth paste or tooth powder. However, cleaning teeth with a miswak or a brush (without paste or powder) is allowed.
(iii) Remaining in the state of Janabah (major impurity) for the whole day.
(iv) Giving blood to anyone.
(v) Quarrelling with someone or abusing him
(vi) Gheebah i.e., to abuse or to blame someone in his absence.
(vii) Telling a lie.
The latter three acts are absolutely prohibited even when one is not in the state of fasting, but they become all the more prohibited when one keeps fast.
Acts Which Are Allowed
The following acts are allowed in the state of fasting :
(i) Cleaning teeth using a miswak or a brush and ears with cotton swabs.
(ii) Applying oil or henna or colour to the hair.
(iii) Using eye-drops or kohl (surma/kajal).
(iv) Wearing perfume or feeling it, or using lipstick or chopstick.
(v) Taking a shower.
(vi) Using medicine through injection.
(vii) Vomiting unintentionally.
(viii) Entrance of smoke or dust into the throat unintentionally.
(ix) Ejaculation while dreaming
(x) Bleeding from the teeth unless blood slips in to the throat.
(xi) Delaying the ghusl of janabah upto the sunrise.
[Taken from “the Month of RAMADAN” by Mufti Muhammad Taqi Usmani]