Hello
Welcome to HealthcareMagic.After exposure to sea water, as your physician rightly diagnosed, can be a fish tank granuloma, where a small abrasion to the skin, gives a portal of entry to the bacteria, and infection begins in the form of small granuloma/ blister which subsequently enlarges and causes a bad ache. It might even cause the lymh nodes to enlarge along its course.A course of antibiotics,(preferably a combination of two-best decided by treating physician) for a long period, about 6 mnths or 1-2 months till the blister/lesion subsides completely.Apart from this kind of granuloma, a sea-lice also can be thought about, which is equally painfull with a local reaction.Then again a swimmer's itch is also a possibility. Well the right diagnosis is basically possible only after seeing. Since your daughter is already on treatment, that means, she must have been diagnosed right. So keep your calm, wait and watch. Hopefully it should subside, if not, then you can think otherwise.Hope your query has been answered well.Wish your daughter a quicker recovery.