May one spray insect repellant into the air on Shabbos?

It is permitted to spray in a way that repels the insects but not in a way that exterminates them. Even though mosquitoes and other flying insects are small and “insignificant” creatures, since they are living creatures it is forbidden to kill them. [1] The gemora [2] stresses this point saying that one who kills a camel on Shabbos, a creature of enormous proportions, [3] and one who kills a flea have violated the biblical prohibition of slaying on Shabbos.

The issue of trapping [4] must also be considered and therefore an avenue of escape, such as an open window, must be provided.

Is it permitted to smear repellent on one’s body?

Yes, it is not medication and is categorically permitted. [5] However, one may not smear soothing ointments or liquids on mosquito bites, [6] as this is the same as taking medication on Shabbos. [7] One may wash or soak the uncomfortable area in water, as that is something that one might do even without having been bitten. [8]

The Shulchan Aruch writes [9] that one may not apply oil to bites in places where smearing oil is not common because it is ‘applying medicine on Shabbos’. However, he adds that one may pour oil onto healthy skin above the sore and the oil will slide onto the sore. Since the oil is applied to healthy skin it is not refuah. [10] Likewise, one is permitted to pour soothing liquid above the affected area, which would slide down onto the bite. Ointments and creams may not be used.

The halacha is different for young children and soothing creams and ointments may be applied directly to bites. Utmost care MUST be taken not to smooth cream and ointments, as it involves a d’oraisso, rather one must use a spoon etc. and place it onto the bite without smoothing.

Similarly, one may use electric mosquito and insect repellants by plugging them into the socket before Shabbos.

What may I do to a mosquito buzzing around my ears?

Besides crying or yelling, nothing much. As stated above, you may use repellent but you may not hit, trap or kill the mosquito.

If it’s biting, must I sit back and watch?

No when it is biting or crawling on your skin you may remove it by hand and throw it out. You may even trap it to throw it out. This is all permitted by Chazal to prevent bodily tza’ar – pain and discomfort. [11] Although a mosquito is muktze, the P’ri Megadim explains that removing it falls under the umbrella of handling a g’raf shel re’i – something vile, which is permitted. [12]

But hearing a buzzing mosquito is also bodily tza’ar , so why is it forbidden to trap it?

Rav Shlomo Zalman Auerbach explained [13] that Chazal only permitted certain actions to prevent actual physical tza’ar not mental tza’ar. [14] Hearing a mosquito buzzing like a dive bomber next to your ear is tantamount to torture, but it is not physical tza’ar. His proof is that we find that if, Hashem yishmor, a house is ablaze (in certain circumstances) one may not extinguish the fire even though the mental anguish is unbearable, yet one may violate a d’rabanan to prevent a mosquito from biting.

A lizard is in the children's bedroom and the children are very frightened, what are my options?

Children's psyche is different to that of adults and in certain cases Chazal permitted violating even a d’oraisso to quell their fears. For example, the gemora (and halacha) says that if a child is locked in a room, one may violate a d’oraisso to extricate him because life is in danger. They understood that a terrified child is endangered.

I don’t know if a lizard in a room is comparable, but one would have to evaluate the situation at hand.

Obviously one may use a broom to ‘sweep’ it out of the room, or use a pan to scoop it up. In both cases one is merely handling muktze, in which case the lizard is a g’raf shel re’i, which may be moved. Trapping is more severe, and if lizards are trapped for their skins, it is far more severe.

How do you deal with a cockroach on Shabbos?

The same as the lizard. It may not be killed, but it may chased out of the room with a broom. Avoid trapping it because it is mental tza’ar – not physical.