Common Herbal Allergens

Mountain Ash (Sorbus spp.) leaves in the rain.

I have often heard it said that herbs can cause 'unexpected' and 'unexplained' reactions for certain individuals. I have read case studies detailing an allergic-type reaction to a specific herb that had been previously well tolerated by the individual reacting. In some cases, these individuals try the herb again in a few months, and find it can again be tolerated. The most common conclusion seems to be simply 'the actions of herbs, as living things, cannot always be explained'.

Throughout my studies, I have found this sentiment repeated across the work of many respected herbalists. I.. have never been able to take 'unexplained' as an answer.

Because of my background in horticulture, the answer to this query seemed relatively straight forward. A pattern begins to emerge when the practice of herbalism is bridged with the studies of plant families, pollen ecology, phytochemistry, and phenology.

Many people live with seasonal allergies. Few people know the specific plant species that cause the allergy. Fewer still are familiar with plant families, and the phytonutrient profiles shared across these families. Yet these relationships matter- and our bodies recognize them, even if we don't.

By identifying the likely culprit of an individual's environmental allergies, it becomes possible to create a practical allergy map of plants that should be treated with greater caution. This DOES NOT mean that every member of a plant family will cause a reaction if one does; nor that every reaction can be predicted through taxonomy alone. Human immune systems are not so tidy. Regardless, this framework is an incredibly valuable tool of safe, responsible herbalism practice.

An apparent 'herbal allergy' is rarely a reaction to the herb in isolation. It is often influenced by the season in which it was harvested, the concentration of pollen present, the part of the plant used, the extraction method, the freshness of the preparation, cross-contamination during harvesting and formulating, or a person's existing level of immune activation (it is worthwhile mentioning here that MCAS is a huge, notable exception. All herbs should be treated with caution by those with MCAS). For example: someone with a ragweed allergy is more likely to be allergic to other members of the Asteraceae family: calendula, feverfew, wormwood, etc. They may be more reactive to certain preparations during late summer and autumn than they are at other times of the year.

This is one of the many reasons why a responsible herbal practice has to go above and beyond 'which herb is good for _____XYZ_____.' A responsible herbalist must go beyond asking about allergies and contraindications. We must consider the individuals unique circumstances to their fullest extent. We must ask if the person has MCAS, asthma, or a history of anaphylaxis. If they have previously reacted to grasses, botanicals, essential oils, foods, fragrances, or topical products. These questions do not eliminate risk. They do, however, allow us to make more informed decisions.

Herbs are complex. So are bodies. But complexity is not mystery. Where patterns exist, we must endeavor to see them.

Common Environmental Allergens

Are you allergic to:

Aspirin/ Salicylates?

You may also react to poplar, willow, strawberries, blackberries, raspberries, blueberries, apples, grapes, peaches, kiwi, plums, oranges, nightshades, radishes, spinach, rosemary, thyme, paprika, dill, wintergreen, sativa cannabis, aloe vera.

Ragweed?

You may also react to calendula, mugwort, sagewort, wormwood, chrysanthemum, feverfew, yarrow, dandelion, sow thistle, sunflower, chamomile, pineapple weed, echinacea, asters, chicory, curry plant, tansy, daisies, thistles, goldenrod, fleabane.

Birch Pollen?

You may also react to apple, peach, cherry, plum, hazelnut, carrot, celery.

Grass Pollen?

You may also react to oatstraw, wheatgrass, barley grass, bamboo.

Resinous trees? Pine, spruce, juniper?

Pine, spruce, fir, cedar, juniper, balsam, frankincense, conifers.

Carrots, Celery?

Celery seed, carrot seed, fennel, anise, dill, coriander, cumin, angelica, lovage, parsley, caraway.

Latex?

Banana, avocado, kiwi, chestnut, papaya.

I am not the first to make this connection; nor is this the most complete guide to herbal allergies. If you are looking for something of the sort, a true deep dive, I would recommend:

Herbal Contraindications and Drug Interactions: Plus Herbal Adjuncts With Medicine, 4th Edition, by Dr. Francis Brinker, N.D.