Redtop seedhead
Plants that are allergenic or that cause dermatitis or mechanical injury are annoying, but the victim usually recovers. Wind-blown pollen generated by trees, grass, plants, and weeds can cause airbone allergies to some people. For the 40-50 million allergy sufferers in America, inhaling airborne allergens can produce a variety of allergic symptoms and because pollen grains are small and buoyant, they can remain airborne for hundreds of miles.
The following is a partial list of weeds that may cause allergic reactions:
| Amaranth, pigweed | Amaranthus spp. |
| Annual bluegrass | Poa annua L. |
| Barnyardgrass | Echinochloa crus-galli (L.) Beauv. |
| Bermudagrass | Cynodon dactylon (L.) Pers. |
| Brome | Bromus spp. |
| Buffalograss | Buchloe dactyloidos (Nutt.) Engelm. |
| Canarygrass | Phalaris spp. |
| Cheat | Bromus secalinus L. |
| Cocklebur | Xanthium spp. |
| Dallisgrass | Paspalum dilatatum Poir. |
| Dandelion | Taraxacum spp. |
| Dock | Rumax spp. |
| Foxtail | Setaria spp. |
| Goatgrass | Aegilops spp. |
| Hemp | Cannabis sativa L. |
| Johnsongrass | Sorghum halepense (L.) Pers. |
| Kochia | Kochia scoparia (L.) Schrad. |
| Lambsquarters | Chenopodium spp. |
| MarsheIder | Iva xanthifolia Nutt. |
| Nettle | Urtica spp. |
| Orchardgrass | Dactylis glomerata L. |
| Plantain | Plantago spp. |
| Quackgrass | Agropyron ripens (L.) Beauv. |
| Red sorrel | Rumex acetosella L. |
| Redtop | Agrostis albaL. |
| Russian thistle | Salsoli kali L. |
| Ryegrass | Lolium multiflorum Lam. |
| Sagebrush | Artemisia spp. |
| Saltbrush | Atriplex spp. |
| Saltgrass | Distichlis spicata (L.) Greene |
| Sudangrass | Sorghum sudanense (Piper) Stapf |
| Velvetgrass, common | Holcus lanatus L. |
| Wormwood | Artemisia spp. |