Common Pigweed (Amaranthus retro?exus) is an insect and wind-pollinated plant that grows 20 to 150 cm in height. It is commonly known as an allergenic weed worldwide due to its capability to produce enormous number of pollen. Pigweed pollen sensitivity may vary across geographical regions, depending on the tested populations diversity. It is considered one of the primary risk factors responsible for inducing respiratory allergies (like allergic rhinitis, allergic rhino-conjunctivitis, and asthma) in sensitive individuals. Pigweed pollen allergens Ama r 1 and Ama r 2 have been identified and listed in the IUIS database. Additionally, Ama r 3, a polcalcin allergenic protein from this pollen, has also been recognized by a study. Pigweed pollen has exhibited cross-reactivity with pollen from other species like lamb’s quarters, Russian thistle, Mesquite, Needle bush, and Burning bush.