Doxy can cause tooth discoloration in kids, so that's why they don't like to use it for kids.
I agree with Simela, best thing to do is get the kid seen by an LLMD.
Chronic Lyme & Bartonella, Gluten & Sulfite Sensitivity, Many Food/Inhalant/Medication/Chemical Allergies & Intolerances, Asthma, Gut issues (dysmotility, non-specific inflammation), UCTD ("Secondary Lupus-Like Syndrome"), Osteoporosis, etc.; G-Tube; TPN via PICC (trying again to wean off the TPN).
Meds: IV Cipro, Heparin (to flush PICC line), Singulair, Claritin, Domperidone, Colloidal Silver, probiotics, digestive enzymes, Milk Thistle & other liver support herbs, Magnesium, Progessence+ (wild yam + essential oils), Moducare, homeopathy.