From the article: How Can My Asthmatic Child Stay Safe on Halloween?
Many children will be outdoors trick-or-treating or attending parties on Halloween this year. Some of these children have asthma, and it is certainly possible for them to experience worsening asthma symptoms while attending these activities. Triggers that are common on Halloween night include cold air, laughter, wearing face masks, exercise, or exposure to allergens such as pollen and pet dander. But taking a few extra precautions will help your asthmatic child enjoy a safe Halloween night. Share your ideas, and learn from others, about how to have a safe Halloween for your asthmatic child.

