Pollen causes allergies because it triggers the body's immune system to mistakenly identify harmless pollen proteins as dangerous invaders. This immune response leads to the production of Immunoglobulin E (IgE) antibodies that bind to defense cells called mast cells, which then release inflammatory substances like histamine. The release of histamine and other chemicals causes allergy symptoms such as sneezing, itching, swelling, and increased mucus production. Additionally, pollen itself contains enzymes called NADPH oxidases that generate reactive oxygen species (ROS), which cause oxidative stress and further provoke the immune system to overreact, intensifying allergic reactions.

How Pollen Causes Allergies

• Pollen grains have water-soluble proteins that are released when they contact mucous membranes.
• In allergic individuals, the immune system overreacts and produces IgE antibodies specific to these proteins.
• IgE antibodies bind to mast cells, causing the release of histamine and other inflammatory chemicals.
• This results in symptoms such as itching, sneezing, runny nose, nasal congestion, and watery eyes.
• Pollen contains NADPH oxidases that create reactive oxygen species (ROS), worsening inflammation and the allergic response.

Immune System Reaction

• The body sees pollen as a threat and activates various immune cells, including neutrophils and eosinophils.
• The released histamine irritates nerve endings, dilates blood vessels, and promotes secretion, leading to typical allergy symptoms.
• Oxidative stress from ROS generated by pollen's enzymes can exacerbate airway inflammation, contributing to conditions like asthma.

Thus, pollen causes allergies because the immune system confuses pollen proteins as harmful, leading to an inflammatory response accompanied by cellular damage from pollen-generated free radicals.