Keep in mind that anything can trigger a mast cell reaction. To find your individual triggers, I recommend journaling your foods and other exposures and looking for trends in symptoms.

Common environmental triggers:

Things you may not be able to immediately control:

exposure to heat and cold
sudden changes in temperature
air pressure changes
air quality problems (but do try air filters)
venom of any kind (of course bee and wasps, but also mosquitoes and small bugs you wouldn’t expect to be able to trigger anaphylactic reactions are common)

They’re a pain, but you will still need to address:

electromagnetic fields, dirty electricity
and, if possible (it isn’t always), hormones (Challenges with menopause and various points in the menstrual cycle are common.)

These things have some work-arounds that might work for you:

triggers in water (pharmaceuticals, chlorine, either consumed or inhaled)- Consider a whole house filter.
scents-including foods (Try avoidance when possible and high grade N99 masks when not.)
vibration, friction
showers and baths
gas stoves
local anesthetics
sleep deprivation
things you touch (When avoidance is impossible, try gloves.)

The (comparably) easy stuff: Say goodbye and don’t look back if you’re triggered by:

tobacco smoke, vaping
chemicals of various kinds, especially in mattresses and furniture

And the three easiest but very common ones people tend to conveniently forget and then deny vehemently until forced to acknowledge they have been making all the worst choices:

cleaning products
body and personal care products (yes, even menstrual pads)
anything you spray anywhere

*If you are a bleach-and-spray-all-the-neurotoxins-and-smelly-laundry-detergent kind of person who has previously not read many labels (or information about why the general population should avoid this kind of thing to begin with), this step will pose an extra challenge for you. Most new mast cell patients who have not been watching these products carefully for some time end up starting from scratch in the above three departments. Fortunately, there are a lot of products out there (see places like Vitacost, if you're in the US) with fewer (and safer) ingredients. Many mast cell patients actually make a number of their own products and find they can get raw ingredients fairly easily and comparably inexpensively.

Common "big" triggers which precipitate "new" or more notably symptomatic mast cell disorders:

If you had one of those “everything went South at once” experiences that “turned on” your MCAS, the following is a short, incomplete list of some common hammer-wielding triggers that tend to do this:

skin/injected testing for allergies
lyme, bartonella, babesiosis, or other tick-borne nastiness
Covid-19 and other viral infections
reactions to drugs or supplements
bacterial infections, ranging from the usual suspects to MRSA
dental procedures
periods of stress
mycotoxin exposure
metal poisoning

Common food triggers:

Keep in mind that it's not always the food. Maybe it’s how it was handled. Maybe it’s what was used to season it or preserve it. Maybe it’s how it was processed. Maybe it’s traces of an antibiotic, growth hormone, or something your food was fed, like...corn! Maybe it’s how old it is, or how ripe. Maybe it’s what was in the water that washed it. Maybe it’s what it was cooked with or around. Maybe it’s how slowly it was cooked. Maybe it’s the fiber in it, or the fat, that’s triggering gastroparesis and mast cells in the stomach.

Also, in the case of foods especially, even an initial reaction to a trigger may not show up for days (especially in the case of "delayed reactions" with bowel movements, which are very common). So look for patterns in your food diary several days out and consider elimination diets of at least a couple weeks.

In the most general terms, as you’re getting started, most mast cell patients require diets which are:

1) Easy to digest (often soft or pureed): Most mast cell patients (and EDS patients) suffer to some extent from delayed motility or gastroparesis. Many patients find putting food in blenders, eating smaller meals, and other common helps for this subdiagnosis are important irrespective of their actual food triggers.

2) Boring (or at least bland): Spicy foods, MSG, artificial colors, and the like are outs pretty much across the board. So is alcohol (also in drugs and other products).

3) Simple: Fewer ingredients means fewer potential triggers and greater chances of identifying these triggers. Preservatives are also a very common issue, as are various chemical pesticides and fertilizers.

Things you probably want to avoid at the start:

1) Your proper allergens as identified by a blood IgE panel: This is always an easy place to start (and remember never to do skin or exposure testing of any kind. There is never an acceptable reason to consider this if there's even an inkling of a thought that you may have a mast cell disorder) in order to rule out allergies which could be causing symptoms.

2) Sodium benzoate and other preservatives, particularly spicy foods, MSG, artificial food colors, and alcohol. (MSG, artificial food colors, sodium benzoate and many other preservatives are excellent things to eliminate from your diet even if you do not have a mast cell disorder.)

3) Histamine liberators: Because these “liberate” histamine from mast cells, you are unlikely to meet a mast cell patient who is friends with shellfish, most nuts (walnuts and cashews seem to top this “no” list), or alcohol. Sadly, on the "for now" list, chocolate, tomatoes, citrus fruits, and strawberries are also histamine liberators and so are relatively common triggers, as well. These later few may well be "stop for now and reevaluate histamine bucket later" things.

3) The very highest histamine foods, many of which also pose other challenges: in addition to the list above, caffeine, pineapple, anything smoked, slow-cooked, pickled, or fermented (including some very aged cheeses and grains, yogurts, etc.), dried fruits, cured meats and deli meats, vinegar, any fish that you did not just catch (even worse if it’s canned), tomato, eggplant, spinach, soy sauce, and other additives and spices.

An extra note on alcohol, just in case you skipped it both times: This is the food item that comes closest to a guarantee. Some patients with active mast cell disorders ONLY have to give up alcohol, but you'd be surprised by how many patients treatment just "doesn't work for" or who have "tried everything" who will not mention immediately to their providers that they continue to drink alcohol (a little counts). So, if this is you, please try to be honest with yourself and with your providers. It’s not just histamine-liberating and high histamine; alcohol also blocks DAO AND decreases tolerances for lower-level allergens and intolerances as they move through the GI tract. This is enough on its own to tip the scales in the wrong direction for mast cell patients eating otherwise tolerated diets.

Beyond these basic cautions, your triggers will be different from those of other mast cell patients, even those whose symptoms are very similar to  yours. Watch your food journal. Keep track of symptoms in any organ system, even several days out, and try to identify patterns.

Common supplement triggers:

Many patients have problems with multivitamin and mineral supplements, perhaps for a number of reasons (the sheer number of ingredients, thiamine being a degranulator, iodine being a common trigger, many having methylation challenges due to certain genetic predispositions...).

Probiotics, including even those which are NOT histamine-producing (many are) and what they are grown on, are also common triggers.

Fermented fish oils, and in many cases fish oils in general, are typically best avoided. There are excellent omega alternatives (see nutritional note on the Treatment page.)

Some well-meaning mast cell patients see practitioners who use IV vitamins to address deficiencies (which are, of course, common with both MCAD and EDS due to malabsorption and other issues) and, foregoing the “start slowly and check the darn ingredients” golden rule, have very dangerous reactions to these treatments. Shotgun-style chelation therapy, as of course would be expected, and other “go big” approaches can also pose significant problems, both in immediate reactions, unexpected “overcorrections,” and dangerous imbalances.

Common Drug Triggers:

I recommend getting in the practice of reading labels and identifying potential triggers in
excipients. In general, simpler formulations are better tolerated than those with many ingredients, especially if these include dyes or preservatives of any kind, but it's possible to have mast cell reactions to ANY excipient.

Many drugs and supplements require compounding in fillers safe for a particular patient (eg rice flour, olive oil, dextrose)

Particularly for supplements, some mast cell patients get along best with pure, third-party tested, pharmaceutical grade powders (just add them to your blended foods). Many mast cell patients react to or have trouble digesting ingredients in pills or capsules of various kinds.

The following is The Mastocytosis Society’s original emergency protocol list of to-be-avoided drugs and some alternatives:

Amphoteracin B
Anticholinergic drugs
Polymyxin B
Vancomycin IV
Alpha-adrenergic blockers
Beta-adrenergic blockers*

*A particular note about beta blockers: these are the only drug class that, on their own, will always make a patient with an active mast cell disorder worse. If it is not immediately life-threatening, a beta antagonist's primary action works against the body's ability to resolve mast cell degranulation in the long term. This is its mechanism of action, not a side effect.

Opioid narcotics
Coedine derivatives
NSAIDS (unless the patient is already taking a drug from this class)

Recommended instead:
Fentanyl, possibly requiring adjunct treatment with Zofran

Muscle Relaxants:

Recommended instead:

Local anesthetics:

Recommended instead (Note: many do not tolerate epinephrine, sulfites, or preservatives in local anesthetics)

RECOMMENDED Interaoperative Induction Meds:

RECOMMENDED inhaled anesthetics:

Contrast agents/dyes, whether iodine-based or not, are extremely common triggers.

Remember that a premedication protocol is recommended for ANY radiology procedure, whether performed with or without contrast agents.