Who should not take hyssop?

Nobody has a research-backed reason to take hyssop, since the human evidence is limited to one small trial in a specific respiratory condition. Several groups have a specific reason for extra caution: anyone pregnant or breastfeeding, anyone with a history of seizures, anyone with an allergy to other mint-family herbs, and anyone considering the essential oil taken internally, which is a separate and higher-risk product from the dried herb.

Pregnant or breastfeeding

If you're pregnant or breastfeeding, talk to a doctor before using hyssop in any form. This is caution copy, not a research finding either way — the one human trial of hyssop excluded pregnant and lactating women, so there's no trial data on hyssop in pregnancy or lactation at all, and traditional herbal sources have long listed hyssop as one to avoid in pregnancy.

A history of seizures or epilepsy

If you have a history of seizures or epilepsy, avoid hyssop essential oil taken internally and ask a doctor before using hyssop in any other form. Hyssop essential oil concentrates pinocamphone, a compound a 2019 systematic review identified as a convulsive agent, and the one human trial of an oral hyssop extract specifically excluded anyone with a seizure history as a precaution.

An allergy to mint-family herbs

Hyssop is in the mint family with sage, peppermint, thyme, lavender and savory. If you're allergic to any of those, treat hyssop with the same caution — the one human trial excluded people with a known allergy to those herbs, and cross-reactivity within a plant family is a reasonable concern even without hyssop-specific allergy data.

Diabetes

The one human trial of oral hyssop excluded people with diabetes. It isn't clear from the study why — the syrup vehicle used in that trial contained sugar, which is its own separate reason for anyone managing blood sugar to check a label rather than assume "hyssop syrup" is sugar-free. Ask a doctor before adding hyssop if you have diabetes.

Liver or kidney disease

There's no published human research on hyssop specifically in people with liver disease or kidney disease. The available liver-safety information (a National Institutes of Health reference monograph) reports hyssop hasn't been implicated in causing liver injury generally, but that isn't the same as a study in people whose liver or kidney function is already impaired. Ask a doctor before using hyssop if either applies to you.

Children

The one human trial of hyssop was conducted in adults; no dosing research exists for children, so this article doesn't offer one.

Questions people ask

Is hyssop safe for kidney problems?

There's no research answer either way — hyssop hasn't been studied in people with kidney disease, so ask a doctor before using it if you have kidney disease.

Related reading: hyssop side effects, hyssop and medications: what to check, and how much hyssop should you take a day?.