Does hyssop cause diarrhea, bloating or constipation?

The one human trial of oral hyssop recorded thirst, dry mouth and throat irritation as its side effects — not diarrhea, bloating or constipation. No trial has isolated any of those three as a measured outcome for hyssop, so there's no research confirming or ruling out a digestive effect either way.

What the one human trial reported

The 2024 randomized trial that gave 60 adults with asthma a hyssop syrup (6 g of extract per dose, twice daily — 12 g/day) or a placebo, for 4 weeks, recorded thirst, dry mouth and throat irritation as side effects in the hyssop group. Five participants — all with a dry cough — stopped taking it because their cough and shortness of breath worsened. Nothing in that trial's published side-effect data mentions diarrhea, bloating or constipation, either as something reported or something specifically checked for.

Hyssop's traditional use for digestion is a separate thing from tested evidence

A National Institutes of Health LiverTox reference describes hyssop as traditionally used "for alleviation of symptoms of gastrointestinal and respiratory tract infections and the common cold." That's a description of traditional use, not a trial result — it doesn't say whether hyssop itself causes, worsens or relieves diarrhea, bloating or constipation, and no dedicated digestive-outcome trial has tested it.

Laxative or constipating effect: neither is established

No published research tests hyssop as a laxative, and none establishes that it reliably causes constipation. If a digestive change shows up after starting hyssop and is new, persistent or bothersome, mentioning it to a doctor is more useful than assuming it's an expected effect — it could also reflect an allergy, since hyssop is in the mint family with sage, peppermint, thyme, lavender and savory. See hyssop side effects for the fuller safety picture.

The nausea question runs the other way

Some of the search traffic behind digestive questions like this one is really asking whether hyssop settles an upset stomach, not whether it causes one. No trial has tested hyssop for nausea, an upset stomach, or a stomach bug — the one published human trial measured asthma-related outcomes (lung function, wheezing, an asthma control score), not a digestive one, so there's nothing in that data to answer the reverse question either.

Tea, extract and the essential oil aren't the same question

Everything above is about the dried herb or the extract syrup tested in the one human trial. Hyssop essential oil is a separate, far more concentrated product that isn't meant to be taken internally at all, so it isn't part of this digestive-effects answer — see hyssop essential oil on skin for what the oil is actually used for.

Questions people ask

Does hyssop tea cause diarrhea?

No trial has tested hyssop tea specifically. The closest data point is the one syrup-extract trial, where thirst, dry mouth and throat irritation were the reported side effects — not diarrhea.

Does hyssop cause bloating?

Bloating wasn't reported in the one published human trial's side-effect data, and no other trial has measured it for hyssop.

Does hyssop cause constipation?

No research establishes hyssop as causing or relieving constipation. There's nothing to report either way.

Related reading: hyssop side effects, hyssop tea, and how much hyssop should you take a day?