**3.8 Pollens**

Pollen is the composition of tiny grains produced by plants for the purpose of fertilization. The wind is the main driver to spread the pollen to different areas, remaining most of the time suspended in the air. It is an important asthma allergen which could exacerbated allergic symptoms such as conjunctivitis, rhinitis and respiratory conditions [34]. Polinization periods are recognized as the peaks in pollen grains in the environment which remain suspended in the air causing allergic symptoms at inhalation. It had been recognized that pollen can be simultaneously combined with air pollution, increasing the changes of asthma and makes particles more easily to breath in. This makes polinization seasons challenging to physicians, making difficult to treat patients most vulnerable to this factor. Pollen season ranges from March to April respectively in which it can last up to 6 months [35]. There are multiple algorithmic maps which shows the percentage of pollen counts around the United States in which it can be characterize as low (0–2.4), low medium (2.5–4.8), medium (4.9–7.2), medium high (7.3–9.6) and high (9.7–12). It's important to understand that dry, windy days can cause allergy symptoms to get worse, however humid and rainy days can sometimes be beneficial to people with allergies. Physiology of this correlates making heavier pollen molecules making it most likely to stay on the ground.
