Hello,
Hives result from dilation of capillaries allowing fluid to leak out into the surrounding tissue, the epidermis.They are of two types:acute and chronic(when hives persist for more than 6 weeks). The most likely triggers for acute urticaria are allergies to pets, horses, latex and foods, such as shellfish and nuts,bee or wasp stings,allergies to medicines,Viral infections, such as glandular fever and herpes, dental and sinus infections, fungal infections, blood transfusions and vaccines.