Papular urticaria is a type of allergic reaction, often related to direct contact with irritants, or bites from mosquitoes, fleas, and other insects. It also relates to an individual's physical constitution; some people are more sensitive and may develop erythema or blisters in response to minor external irritants. This condition is also linked to one's home environment, such as frequently keeping pets or not regularly sunning beddings, which might harbor mold and mites. Once the condition occurs, it is advisable to regularly disinfect and sun-expose bedding, avoid contact with small animals, and stay away from parks or areas with dense vegetation. Topical application of anti-allergic medications can treat the condition. (Note: The doctor's answer is for reference only. Medications should be taken under the guidance of a professional physician, and self-medication should be avoided.)