TL;DR:  I got the vaccine 3/20. In May, I was diagnosed with mast cell activation. My doctor thought it was triggered by the vaccine. In April, I was diagnosed with asthma and a polyethylene glycol allergy. I had no prior history of asthma or other unusual breathing problems ever. Within 15 min of getting the vaccine, I had shortness of breath. From 1-4 hours after getting the vaccine, I had shortness of breath, heaviness, dissociation, brain fog, lethargy, mood swings, and nausea. 10 hours after getting the vaccine, I had a small rash on my left wrist. From 3/20 to the present, I have had asthma and mast cell activation symptoms that have not been completely alleviated by medication or time. I can now walk for up to 30 minutes before I run out of breath, and I cannot walk up moderately steep hills.  Full report:  Fifteen minutes after getting the Pfizer vaccine on 3/20, it felt noticeably difficult to breathe while walking across the parking lot. I took off my mask, but it still felt hard to breathe. I waited in my friend's convertible for 15 minutes and nothing got worse, so I went home. From one to four hours after getting vaccinated, it felt somewhat difficult to breathe at rest as well, and I was dizzy enough that it was hard to walk in a straight line, though I didn't feel like I was in any danger.  I do have an EpiPen and Benadryl on hand if I were to need it, and live with roommates who can drive me to the hospital.  During those four hours, I also felt how I feel around dust, which I do have an allergy to: very lethargic, brain fog, dissociation, heaviness, etc. I didn't have hives, a rash, swollen face or lips, increased HR, or any other typical allergy symptoms during those four hours. My breathing passageway did not feel swollen shut. I was also somewhat nauseous and had odd mood swings.  At about ten hours after getting the vaccine, I took a picture of a small blistery rash on my wrist. It went away within a few days.  The next day (Sunday), I was no longer feeling lethargic and took a walk. I was walking up a hill, as I did every day or so, and I had to stop every 10-20 seconds because I felt like I couldn't breathe enough. I was able to open the back of my throat and take a deep breath, but it didn't feel like I was getting enough air. I also felt air hunger for about ten minutes after getting home and sitting down. (This pattern has continued since then. The air hunger after getting home from a walk lasted for a few months.)  This all felt  identical to what I would feel in high school sometimes, while running long distances. I had trouble breathing for maybe a few minutes total over the course of a few years. My dad thought it was exercise-induced asthma back then. However, I have never been diagnosed with asthma and have never had breathing problems otherwise. I get upper respiratory infections less often than my healthy peers.  For 1-2 months after getting the vaccine, I noticed I would suddenly get extremely tired in the evening. In retrospect, this was probably a mast cell activation response in response to eating my dinner. (As mentioned later, I was diagnosed with mast cell activation, as triggered by the vaccine.)  ~~  As of April, it was still hard to breathe, most significantly if I tried to take a walk and for some time afterwards.  My breathing would sometimes feel constricted at rest as well, like if I haven't used the steroid inhaler in 12+ hours, or after I took a shower on 4/7. Benadryl helped when I used it. I took Allegra or Zyrtec every day, but they did not help much.  My doctor gave me an Albuterol inhaler which didn't seem to do anything at first, though it did help somewhat once I got a spacer. I started using a steroid inhaler every 12 hours in early April, which also helped somewhat, but did not solve the problem. I was diagnosed with asthma in April or May.  I have mild/moderate allergies to dust, mold, and certain pollens, as diagnosed by an allergist in 2019, but there's never been any breathing involvement. I've never had a vaccine or drug reaction, other than maybe a sore arm, and I get the flu shot every year. I got the HPV vaccines last year.  I have a pulse oximeter, and my blood oxygen randomly hit 93% like 10% of the time when I was at rest for the first two weeks after getting the vaccine, and on 4/7 after showering. I've worn the device on and off for maybe an hour total since 3/20.  I had some degree of (harmless) skipped heartbeats before getting the vaccine. I had skipped heartbeats that were much more frequent in 2017. For two weeks after getting the vaccine, my heart was skipping very noticeably more often, perhaps as often as in 2017. (I had been checked out by a cardiologist in 2017 and he said I was safe. I went to urgent care in Jan 2021 during a brief increase in skipped heartbeats, and they said I was safe.)  ~~  My allergist did an oral challenge for polyethylene glycol in late April or early May. (PEG is an ingredient in the vaccine.) I went off all antihistamines for 12 days before doing the allergy challenge. First he did a skinprick test, but it was negative, including to the control. I took the tiniest dose (1g of Miralax) and reacted to it for 2+ hours. The typical adult dose of Miralax is 17g. I had difficulty breathing, difficulty walking, heaviness, etc. My doctor wanted to give me a shot of epinephrine and told me not to get another shot with PEG in the ingredients until we could do a desensitization procedure.  After doing the allergy challenge, I reacted to all foods within 10-20 minutes of eating them. (I also reacted to high histamine foods starting 9 days after going off antihistamines in April. This had never happened before.) I asked a doctor for Cromolyn, and it helped tremendously with reducing reactions to food. After doing the polyethylene glycol oral challenge, I had to stop taking most meds with polyethylene glycol (even though I had previously tolerated them), such as Zyrtec and Allegra.  I ran out of Cromolyn for 24 hours in April. I ate an avocado and had a migraine. I have been intermittently sensitive to light since then, but especially for one month afterwards.  I saw a different doctor in May, and he diagnosed me with mast cell activation as triggered by the vaccine. He know of two other people who had this response, though they recovered within a few weeks. He prescribed me a number of mast cell stabilizers and antihistamines, and they help to some degree. I now take Cromolyn 10mL 4x/day, QVAR 80mcg steroid inhaler 2x/day, Ketotifen 1mg 2x/day, Claritin 3x/day, Pepcid AC 2x/day, and a number of supplements.  I suspect I may have had a mild case of mast cell activation for years, though, due to my reactions to dust, mold, scented products, east coast pollen, and a handful of foods. (I would get heavy, dissociated, lethargic, brain fog, etc.) Also, when I got the vaccine, I had 5 rashes that had been there for about 2 months, and my eyelids had been pink and peeling for at least a month. My psoriasis was also very bad - it was only ever that bad briefly in 2017.  ~~  It's now September. I still have many of the symptoms I have since March, namely asthma and mast cell activation. I still cannot climb the hill by my house without stopping many times, as it gets too hard to breathe. I still need to take Cromolyn, Ketotifen, Claritin, and QVAR just as often as when I began taking them this spring. On a good day, I can walk for about half an hour and can eat 30 foods without reacting to them. (Aside from bread and crackers, all other safe foods are pretty much a single ingredient.) Before I got the vaccine, I could walk for 1 - 1.5 hours at a time and didn't have to stop because of breathing issues. I no longer have regular rashes or red/peeling eyelids, and I am not sensitive to light as often.