There are three types of pollen that commonly cause hay fever; grass pollen, tree pollen and weed pollen. The majority of people with hay fever (90%) suffer with an allergy to grass pollen whereas only 25% suffer an allergy to tree pollen and an even smaller minority to weed pollen.

Hay fever season is usually from sometime in March until September. However, different types of pollen may circulate at different times of the year. For example, tree pollen season is usually from late March to mid-May, whereas grass pollen is worse from mid-May to July. Grass pollen from mid-May through to July. Weed pollen normally occurs the latest in the year from the end of June to September.

A dental infection occurs when bacteria invade the soft tissue in the mouth, leading to inflammation, pain, and potential damage to surrounding structures. Common types of dental infections include abscesses, which may develop at the tooth's root or in the gums.