At the time of the injection (4/3/2021) I experienced just the normal redness warmth soreness for a couple of days.   At the end of the month 4/29/21 I began experiencing  daily itching on my scalp, stomach, legs, stomach cramps (occasional), gagging and vomiting (at least one time daily).  At first my doctor and I thought it might be related to a recent change in thyroid from NP thyroid to a compounded thyroid so I was switched back to the NP Thyroid and dropped all supplements except the Magnesium Citrate and Carditone.  No change.  Antihistamines (Chlortab, generic for Chlorpheniramine Maleate) didn't help. The doctor scheduled me for an EGD (7/28/21) and then a pelvic ultrasound (8/20/21) to rule out cancer, etc..  Everything was clear/negative.  I was continuing to have these symptoms.  Still having symptoms I had my blood drawn on 10/21/21 for an MRT blood test which looks at foods that I would be reactive to, especially histamines.   I received my report and reviewed it with the dietician and on 11/14/21 began an extremely limited diet in which I was to slowly begin testing/adding back in foods (3 categories ? 0 to minimally reactive, moderately reactive, and severley reactive) with some I could not test/try for 3 or 6 months.  Immediately when I began this extremely limited diet my symptoms mostly disappeared with exception of some inconsistent mild itching.  (I was already consistently avoiding wheat/gluten products beginning in 2005 as a result of itchy rashes when I ate such foods). I have experienced some of the original symptoms off and on as I have tested various foods and some foods/ingredients I thought I were okay with have turned out to be troublesome and eliminated again from my diet.  Some of the foods shown to be moderately or severely reactive on the MRT were foods that were routine to our diet that I had never had any problems with.   As of 1/25/22 I was having some occasional itching but the gagging/vomiting seemed limited to certain foods to be retested at a later date.   Suspicion at that time was that the Pfizer vaccine dose #2 worked so well on my immune system that it sent me into immunity overdrive. On 2/28/22 I saw a dermatologist.  Labs ordered to look for underlying cause.  All labs were clear.  Prescribed Triamcinolone 0.1% cream for itchy/rash areas.  Recommended use of Loratadine 10 mg tablets (1 per 24 hours) and prn Benadryl 25 mg tablets. On 3/9/22 I saw my ND,  who scheduled me for blood tests on 3/11/22.  On 3/9/22 she stated she was not formally diagnosing me with MCAS (Mast Cell Activation Syndrome) but that was what it looked like to her.  She explained that the gastrointestinal issues (stomach cramps, gagging and vomiting, etc) were histamine responses just like the itching. At that time she started me on Aller-C, two capsules before every meal, which was supposed to tamp down the mast cell response to the foods I eat with the hope that I could more foods back into my minimal diet.  The blood test results showed that my Eosinophils was higher than the normal range (5.1) and this was 11 months after the vaccine #2 (4/3/21).   Continuing as of 5/8/22 to have the itching and occasional gagging/vomiting/stomach cramps and eating a very minimal diet, using the Aller-C to be able to eat at all.