Pigweed is one of the most prevalent and persistent fall allergens found throughout Arizona, thriving in the same disturbed soil environments that support ragweed and Russian Thistle. Pigweed allergies are also known as Lamb’s Quarters in some regions and produce heavy pollen that can induce hay fever or asthma, making it one of several allergenic weeds active in Arizona during the fall. Several species fall under this common name, with Palmer’s Amaranth being particularly significant for Arizona residents.
Palmer’s Amaranth, also known as pigweed, has a widespread distribution across the United States, with the Southwest region including Arizona and New Mexico harboring this allergen. The plant’s growth generally begins in early spring, often as soon as March, continuing throughout the hot summer months, with seeds typically germinating once soil temperatures reach around 68 degrees Fahrenheit and the plant releasing pollen as it reaches maturity by late summer.
This extended growing season is particularly relevant for Arizona. The specific climate of Arizona can often exacerbate certain allergies, as the desert air can carry pollen further and the state’s often warm weather allows for a longer growing season, meaning longer exposure to allergenic plants. In pollen counts, pigweed is often interchanged with the plant called lamb’s quarters since flowering and pollen shed occur at the same time and the pollen grains look identical to analysts conducting pollen counts through microscopes, with late summer to autumn usually being the peak time for pollen shed.
Cross-reactivity is extensive within this group. Cross-reactivity can occur with pigweed allergy as it shares similar proteins with other plants, particularly in the Amaranthaceae family, which may cause allergic reactions to related weeds like lamb’s quarters and goosefoot, and some individuals might also experience cross-reactivity to food items like beets and spinach due to their botanical relationship.
Because pigweed is an aggressive agricultural and landscape weed, it is never recommended for intentional planting, and most exposure in Arizona comes from uncontrolled growth along roadsides, vacant lots, and field margins rather than deliberate cultivation.
If your symptoms intensify through late summer and into fall, pigweed could be a significant contributor alongside ragweed and Russian Thistle. The team at Carefree Allergy can confirm your specific triggers through targeted testing and build a treatment plan tailored to your needs. Options range from medication management to long-term immunotherapy to reduce your sensitivity to pigweed and the other fall weeds active across Arizona each year.
