| Infections |
| Viral |
| Parasitic |
| Bacterial |
| IgE-mediated allergic cases |
| Medications |
| Insects |
| Stinging (yellow jackets, bees, wasps, hornets, fire ants) |
| Biting (Triatoma [kissing bugs]) |
| Foods |
| Blood products (urticarial transfusion reaction) |
| Latex (contact or inhaled) |
| Contact allergens (animal saliva, raw foods) |
| Aeroallergens (rare) |
| Food additives |
| Direct mast cell activation |
| Narcotics/opiates |
| Muscle relaxants (eg, succinylcholine) |
| Radiocontrast agents |
| Vancomycin |
| Physical stimuli |
| Dermatographism |
| Delayed pressure |
| Cold |
| Cholinergic |
| Vibratory |
| Aquagenic |
| Solar |
| Exertion/exercise |
| Miscellaneous mechanisms |
| Nonsteroidal anti-inflammatory drugs |
| Serum sickness |
| Transfusion reactions (distinct from IgE-mediated reactions) |
| Hormone-associated (progesterone) |
| Stinging nettle |
