We conducted a survey on 195 respondents with HIT and / or MCAS to find out which products they’re using to manage their condition. The most commonly used supplements and their benefits are listed below:


Quercetin is a plant pigment (called a flavonoid) found in plants and many fruits and vegetables such as apples, berries, grapes, capers, onions, shallots, green tea, as well as many seeds and nuts (Li et al., 2016). Quercetin has been shown to have anti-inflammatory and anti-allergic properties. It has also been shown to stabilize mast cells. Quercetin can also be taken in the form of supplements, which may be preferable for people suffering with HIT and MCAS as many of the foods containing quercetin are also high in histamine.

Vitamin C

Vitamin C naturally boosts the immune system and also acts as an antihistamine. One study investigated the impact of intravenous vitamin C in the treatment of allergies and found a significant decline in the symptoms. Vitamin C is present naturally in foods such as citrus fruits, bell peppers, broccoli, cauliflower, and tomatoes among others. Some of these foods are also high in histamine so if you’re adhering to a low histamine diet, you may prefer taking Vitamin C supplements. 

Vitamin D

Vitamin D has been shown to stabilize mast cells and act as an anti-inflammatory. Research has found that taking vitamin D in conjunction with antihistamines and corticosteroids may also improve chronic hives. High levels of vitamin D however, can have a negative impact on your body, and the Institute of Medicine recommends between 20 to 50 ng/mL.


One of the primary root causes for histamine intolerance and mast cell activation syndrome is improper gut health. Probiotics are live bacteria and yeast that can help to improve your digestive system by restoring the natural balance of your gut. However, many probiotics contain histamine and may cause a reaction amongst people with HIT and MCAS. It is therefore important to identify which probiotics contain histamine before trying any. Everyone’s gut bacteria is unique and people may respond to the same probiotic in very different ways. It will take a process of trial and error before discovering which one is right for you.

Diamine Oxidase

Diamine oxidase (DAO) is the main enzyme that breaks down histamine in your body and is found in the small intestine. When DAO is adequate or functioning, it is estimated to break down 99% of the histamine that enters the body. When DAO is deficient, this excess histamine will build up in the body, causing an overflow of your histamine bucket and resulting in allergy-like symptoms. You can increase the levels of DAO in your body naturally by  consuming foods with nutrients such as omega-3 fatty acids, saturated fat, calcium, zinc and magnesium, among others. Foods such as olive oil, walnuts, fresh fish, nuts, and certain vegetables help to boost the levels of DAO in your body. Additionally, it’s important to avoid DAO-blocking foods such as alcohol, energy drinks and certain teas (black, mate and green teas). As some of the DAO-boosting foods are high in histamine, you can also take a number of supplements that are available without a prescription. It is important to note that taking a DAO supplement will not increase your internal DAO but may help to break down the histamine that you consume in food. Therefore, DAO supplements will not cure your histamine intolerance but will simply help to reduce your histamine bucket but reducing the amount of histamine entering your body from food.


Magnesium is needed for over 300 biochemical reactions in the body including bone strength, maintaining normal nerve and muscle function, and supporting a healthy immune system. Studies have linked magnesium deficiency in animals with rising levels of histamine as well as increased mast cells. Food sources that are high in magnesium include green, leafy vegetables, nuts and seeds, certain fruits such as bananas, avocados and raspberries, green vegetables such as broccoli, peas, green beans, and fish such as salmon, mackerel and tuna, among others. Magnesium can also be taken in the form of supplements as well as transdermal through creams, oils, sprays and bath salts. There are side-effects from the intake of excess magnesium so be careful when consuming supplements. The recommended daily requirements for adult women is between 310 to 320 mg and 400 to 420 mg for adult males.


Bromelain is a mixture of enzymes found in pineapples and is used as a natural remedy for inflammation due to its anti-inflammatory and anti-allergic properties. It is used as a supplement for nasal swelling, muscle swelling, and poor digestion while topical bromelain is used for wounds and burns. Please avoid taking bromelain if you are allergic to pineapples.

As always, please consult a medical professional before making any changes to your diet or medical protocol.


Hattori, M. et al. (2013) ‘Quercetin inhibits transcriptional up-regulation of histamine H1 receptor via suppressing protein kinase C-δ/extracellular signal-regulated kinase/poly(ADP-ribose) polymerase-1 signaling pathway in HeLa cells’, International Immunopharmacology, 15(2), pp. 232–239. doi: 10.1016/j.intimp.2012.12.030.

Institute of Medicine (US) Committee to Review Dietary Reference Intakes for Vitamin D and Calcium (2011) Dietary Reference Intakes for Calcium and Vitamin D. Edited by A. C. Ross et al. Washington (DC): National Academies Press (US) (The National Academies Collection: Reports funded by National Institutes of Health). Available at: http://www.ncbi.nlm.nih.gov/books/NBK56070/ (Accessed: 5 November 2019).

Li, Y. et al. (2016) ‘Quercetin, Inflammation and Immunity’, Nutrients, 8(3). doi: 10.3390/nu8030167.

Liu, Z.-Q. et al. (2017) ‘Vitamin D contributes to mast cell stabilization’, Allergy, 72(8), pp. 1184–1192. doi: 10.1111/all.13110.

Nishio, A., Ishiguro, S. and Miyao, N. (1987) ‘Specific change of histamine metabolism in acute magnesium-deficient young rats’, Drug-Nutrient Interactions, 5(2), pp. 89–96.

Rogerio, A. P. et al. (2007) ‘Anti-inflammatory activity of quercetin and isoquercitrin in experimental murine allergic asthma’, Inflammation Research: Official Journal of the European Histamine Research Society … [et Al.], 56(10), pp. 402–408. doi: 10.1007/s00011-007-7005-6.

Secor, E. R. et al. (2013) ‘Bromelain Inhibits Allergic Sensitization and Murine Asthma via Modulation of Dendritic Cells’, Evidence-based Complementary and Alternative Medicine : eCAM, 2013. doi: 10.1155/2013/702196.

Weng, Z. et al. (2012) ‘Quercetin Is More Effective than Cromolyn in Blocking Human Mast Cell Cytokine Release and Inhibits Contact Dermatitis and Photosensitivity in Humans’, PLoS ONE, 7(3). doi: 10.1371/journal.pone.0033805.