An in-depth knowledge of allergen cross-reactivity is imperative when selecting allergens for immunotherapy. Because limiting the number of allergens in a vaccine preparation may be necessary to achieve the optimal therapeutic dose for each allergen, the cross-reactivity of clinically relevant allergens should be taken into account when making allergen selections. When cross-reactivity between pollens is substantial, selection of a single pollen within the cross-reactive genus or subfamily may suffice.

The recognition of distinct antigens by the same IgE antibody, cross-reactivity is demonstrable by in vivo and in vitro tests, and clinically manifests as reactions caused by antigens homologous to different species.

Led by resident botanist Dan Mork, we’ve put together a handy reference chart identifying known patterns of allergen cross-reactivity. View below or download and print.

This guide illustrates the cross reactive qualities of some grasses, weeds, and trees from the HollisterStier pollen allergen lines. If you have more questions on cross reactivity please contact our customer service center to be connected with our botanist. To make identifying the correct HollisterStier product, the item number of the allergen is provided to reference when posing questions or placing orders.


Redtop 0777
Bent Grass, Colonial
Koeler’s Grass
Oats, Common Wild
Oatgrass, Tall

Bent Grass
Bluegrass, Kentucky & Canada
Canary Grass
Reed Canary Grass
Quack Grass

Orchard Grass 0718
Cheat Brome
Blue Bunchgrass
Wheatgrass, Crested
Wheatgrass, Western
Giant Wild Ryegrass
Rye, Cultivated
Rye, Alkali

Quack Grass
Ryegrass, Italian

Gamma Grass, Blue
Salt Grass

Sorghum, Common Cultivated
Sudan Grass


Dock, Bitter
Dock, Yellow
Sheep Sorrel

Plantain, Narrowleaf
Plantain, Broadleaf

Sea Blite, Alkali

Giant Ragweed 2294

Short Ragweed 2297
Ragweed, Slender
Ragweed, Southern


Western Ragweed 2309
Beach Bur
Ragweed, Bur/Rabbit Bush
Ragweed, Canyon
Ragweed, Desert
Ragweed, False
Ragweed, Silver

Mexican Tea
Jerusalem Oak

Pigweed, Spiny
Waterhemp, Western
Prostrate Pigweed

Iodine Bush
Saltbush, Annual
Scale, All
Scale, Bract
Scale, Brewer’s
Scale, Lens
Scale, Red
Scale, Silver
Scale, Spear
Sugar Beet
Winter Fat

Sage, Annual
Sage, Coast
Sage, Common
Sage, Fringe
Sage, Pasture
Sage, Sand Dune
Sage, Tarregon/Green
Sage, White
Sage, Wormwood


Acacia, Bailey’s

Alder, Hazel
Alder, Mountain
Alder, Sitka
Alder, White

Ash, Arizona
Ash, Green
Ash, Oregon

Birch, Cherry
Birch, Paper
Birch, River/Red
Birch, Spring
Birch, White
Birch, Yellow
Chestnut, American
Hazelnut, American
Hazelnut, European
Hornbeam, American

Chestnut, Horse
Maple, Coast
Maple, Red
Maple, Soft Silver
Maple, Sugar

Arborvitae, Oriental
Cedar, Giant/Western Red
Cedar, Incense
Cedar, Japanese
Cedar, Rocky Mountain
Cedar, White
Juniper, California
Juniper, Chinese
Juniper, One-seed
Juniper, Pinchot
Juniper, Utah
Juniper, Western

Cedar, Port Orford
Cypress, Italian
Cypress, Monterey

Cottonwood, Black
Cottonwood, Eastern
Cottonwood, Fremont
Cottonwood, Great Plains
Poplar, Balsam
Poplar, Lombardy
Poplar, White

Oak, Arizona, Gambel
Oak, Arizona Scrub
Oak, Blackjack
Oak, Bur
Oak, California Black
Oak, California Live
Oak, California Scrub
Oak, Coast Live
Oak, Englemann
Oak, Garry/Oregon
Oak, Holly
Oak, Interior Live
Oak, Post
Oak, Swamp/Pin
Oak, Valley
Oak, Virginia Live
Oak, Water

Elm, Chinese 1547
Elm, Fall-Blooming

Elm, Siberian
Elm, Slippery

Hickory, Shellbark
Hickory, White

Pine, Austrian
Pine, Digger
Pine, Loblolly
Pine, Longleaf
Pine, Monterey
Pine, Pinyon
Pine, Red
Pine, Shortleaf
Pine, Virginia Scrub
Pine, Eastern White
Pine, Western White

Sycamore, Mapleleaf
Sycamore, Western

Walnut, Arizona
Walnut, Hind’s California Black
Walnut, English

Willow, Arroyo
Willow, Pussy
Willow, Red
Willow, Yellow