Weeds are often classified as undesirable plants that disrupt cultivated areas, but they also pose significant health risks to humans and livestock. This review examines the diverse impacts of weed pollen, focusing on allergenic properties, health risks, and effects on domestic animals. Weeds, such as ragweed, mugwort, feverfew, and plantain, are known to produce potent allergens that contribute to various allergic conditions in humans, including allergic rhinitis, asthma, and contact dermatitis. The review discusses major allergenic proteins found in weed pollen, including pectate lyases, defensin-like proteins, Ole e 1-like proteins, and non-specific lipid transfer proteins, as well as panallergens such as profilins and calcium-binding proteins that cause cross-reactivity among sensitized individuals. Additionally, it highlights the health risks associated with inhaling or ingesting pollen contaminated with toxic compounds. These risks include respiratory distress, food poisoning, and adverse effects on livestock, such as reduced feed intake and weight loss. The review underscores the significance of understanding the allergenic and toxic properties of weed pollen and their impact on human health and livestock.