AllergyMD patient-reference library

Common allergens in Southwest Missouri

A practical guide to the outdoor and indoor allergens that matter here, and the environmental steps that actually help.

Seasonal (outdoor) allergens are present during defined parts of the year. Which plants pollinate, and when, varies a lot across the country. The outdoor allergens allergists test for in this region are the ones that matter in Southwest Missouri. Timing follows a consistent pattern each year, but levels swing with rainfall, humidity, wind, and temperature.

Tree pollen

Tree pollen is produced in late winter and spring. Counts can get very high in the spring, and that is the cause of most spring allergy symptoms.

Cedar — Late winter / early spring. Locally, red cedar is most common. Mountain cedar, which cross-reacts, can blow in from hundreds of miles away (Texas, Oklahoma, and Colorado). As early as late January or February, pollen produced farther south can cause symptoms here.

Ash, birch, elm, maple, cottonwood — Early spring. March and April are typically the peak.

Oak, hickory, cottonwood, sycamore, walnut, pecan — Mid to late spring. Oak is the most prolific tree-pollen producer in Southwest Missouri. It usually peaks around April but can show up earlier. Tree-pollen season can persist into May.

Trees with large, colorful, showy flowers — dogwoods, Bradford pears, cherry, redbud, crabapples — bloom at the same time as many of the trees above and do not cause allergies. They are insect-pollinated, not wind-pollinated, so they do not put a large amount of pollen into the air.

Grass pollen

Grass season is summer, starting in May and lasting through August. The pollen causes allergies, not the grass itself. Grass species fall into two broad groups, northern and southern. There is a large amount of cross-reactivity within each group, so allergy to one often means reaction to others in the same group.

Northern grasses — Fescue, timothy, Johnson. Fescue is the most common grass in Southwest Missouri, used in lawns and pastures.

Southern grasses — Bermuda grass is the most important pollinator in this group.

Weed pollen

Weeds produce the most pollen in the fall, though some pollinate in mid and late summer too. Ragweed is the undisputed king of this group, but several other weeds put out large amounts of allergenic pollen and can be a major problem on their own.

Ragweed — Pollinates from August until the first hard frost. Very common in fields and pasture, especially disturbed land. Ragweed pollen can blow from hundreds of miles away. Goldenrod blooms at the same time and gets blamed; it is not the main fall pollen here.

English plantain, pigweed, dock/sorrel, lambsquarters, marshelder, Russian thistle, kochia — These all produce large amounts of windborne pollen that can cause allergies.

Outdoor mold

Outdoor molds grow in soil and dead vegetation and produce highly allergenic spores that become airborne. They proliferate with damp weather. Levels are highest in the warmer months, but they can be found outdoors during warm spells in winter. Mowing can kick up large amounts of mold spores and cause severe problems that are sometimes blamed on grass allergy. Mold allergy tends to be especially severe in people who also have asthma.

Alternaria and Cladosporium — These two outdoor molds reach the highest levels and are the most important outdoor mold allergens. At times, mold counts can get extremely high.

Helminthosporium, Epicoccum, Fusarium, Cephalosporium, Curvularia — Other important allergy-producing mold species.

Avoiding outdoor allergens

Year-round (perennial / indoor) allergens

These are present throughout the year indoors.

Dust mite — Microscopic mites that live everywhere humans do. They cannot be eliminated completely; they are in the cleanest homes. They live in mattresses, pillows, carpet, upholstered furniture, stuffed animals, and the like. They produce a highly allergenic protein that is the major allergen in household dust. Minimizing contact can improve symptoms. Focus on the bedroom first — that is where exposure is largest.

Dog dander, cat dander — Many people do not realize they are allergic to their own pets. Even after a pet has been in the home for a long time, new allergy can still develop.

Indoor mold — The most important indoor species are Aspergillus and Penicillium. They grow if there are damp spaces or excessive humidity, especially in basements, bathrooms, and closets. Indoor mold is usually not a hidden problem: wet drywall or damp basement walls, especially if the space smells musty, usually means significant growth.

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