<s>[INST] My doctor started my 10 year old daughter on Zoloft, sertraline really, and the next day after starting it, she has now this quarter sized lump under her chin, like under her tongue but on the outside of her throat, not inside, and it's very painful to the touch and hard, I felt it. Is she having an allergic reaction? She isn't having difficulty breathing but the lump is so painful it hurts to put too much pressure on it. She started the Zoloft medication on 5/9/11. [/INST] Hi,Dear thanks for the query to HCM.Cause of the lump under chin of your daughter is -as follows-a-Zoloft is known to cause skin rash.But what you describe is a solo-pimple like / or insect bite like lump under the chin.Allergic reaction is remote possibility but insectbite?spider?is the most probable cause of that lump.Hope this would help your worry to take proper steps for health of your daughter.Wellcome again if you have any more query in this regard.Have a Good Day. </s>