If a mother is smoking during pregnancy, the child has a higher risk of having allergic eczema. Tobacco is the worst and most air pollutant and it causes allergies and asthma. Parental smoking also increases the risk of children of having allergies. Pollen allergy is mostly common to those in Japanese cities. Allergic disease is also common in countries such as North America and Europe .The main indoor allergies are mold, dust, and fungi. When you try to air out these allergens, you get more in. Mold can be in side or out so if you try to air it out you just airing it in. Also, if you put your clothes out to dry, they get mold on them and bring it in your house.