Inclusion
Participants must meet all the following criteria:
* Adults, at least 21 years of age at the time of electronic consent, inclusive of all ethnicities, races, and gender identities
* Assigned sex at birth will determine sex-specific recruitment and PROs (male vs female) employed, when needed
* Resides in the United States
* Report histamine intolerance symptoms affecting GI health and at least one other organ/system, determined from the Histamine Intolerance Checklist
* Has the opportunity for at least 30% improvement in their primary health outcome
* Expresses a willingness to take a study product and not know the product identity (active or placebo) until the end of the study
Exclusion
Individuals who report any of the following during screening may be excluded from participation.
* Report being pregnant, trying to become pregnant, or breastfeeding
* Unable to provide a valid US shipping address and mobile phone number
* Reports current enrollment in another clinical trial
* Reports being a heavy drinker (defined as drinking 3 or more alcoholic beverages per day)
* Unable to read and understand English at a 7th grade level
* Reports a current and/or recent (up to 3 months ago) major illness and/or surgery that poses a known, significant safety risk.
* Reports a diagnosis of cardiac dysfunction, liver or kidney disease that presents a known contraindication and/or a significant safety risk with any of the study product ingredients. This may include:
* NYHA Class III or IV congestive heart failure, atrial fibrillation, uncontrolled arrhythmias, cirrhosis, end-stage liver disease, stage 3b or 4 chronic kidney disease, or kidney failure
* Reports taking medications that have a well-established moderate or severe interaction, posing a substantial safety risk with any of the study product ingredients. This may include:
* Anticoagulants, antihypertensives, anxiolytics, antidepressants, chemotherapy, immunotherapy, sedative hypnotics, seizure medications, medications that warn against grapefruit consumption, corticosteroids at doses greater than 5 mg per day, diabetic medications, oral anti-infectives (antibiotics, antifungals, antivirals) to treat an acute infection, antipsychotics, MAOIs, or thyroid products
* Reports current use of the primary ingredient(s) and/or similar product(s) to the active study product(s) that may limit the effects of the study products and/or pose a safety risk
* Lack of reliable daily access to the internet
