No timer for gas and giggles for my child sim

What kind of mods are you using ? Could be a conflict.

Do you have timers on other sick moodlets ? I honestly never pay attention to that.

You can try going traveling or moving Sim out and back in to see if that solves it.

If not. you need TwistedMexis AllCheats mod, then use the cheat Sims.remove_all_buffs

This will remove all current moodlets. You can also just remove that one but I'm not sure what the name of it is.