When do you know it's time to switch H1 antihistamines?

MCASMike

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Well it looks like the adrenaline rush with high pulse that I experienced during the middle of the night a month ago was due to the loratidine no longer working. I've also had a really bad runny nose for over a week now. Yesterday, right after I finished breakfast, my pulse rose to the 170s and I was just sitting there, not doing much of anything (I did eat an egg so perhaps the white of the egg was too much in terms of histamines). The cardiologist wouldn't see me but the PCP would, and he didn't know much if anything about MCAS at first but looked it up on Google (he said, "I don't think you have mastocystitis" at first). He said you'd be itchy and I have been itchy, mostly at night, especially when it's warmer. Then he mentioned rashes and I told him I get rashes for no reason that go away quickly, and mentioned the dermatographia, which he then tested me for and that seemed to convince him.

Anyway, he thought montelukast would help for some reason, so I took one last night and didn't have post-nasal drip or runny nose, but of course the most important thing is getting the pulse down. So far, it hasn't gotten back up the 170s, but if I move around it will go into the 120s at least. At rest the best so far is the low to mid 90s, whereas around 90 used to be my normal (and the cardiologist thought that was okay, a few years back). About a month ago I was able to walk up two flights of steps without a problem and now I have to move slowly in order to avoid the pulse rise. I have started to take some old Antivert I had just so I have one antihistamine at work, but I intend to order cetirizine and fexfenadine. I've read that if I wait a couple weeks, the loratidine may be effective again:

https://www.healthline.com/health/ciu/when-antihistamines-stop-working#natural-remedies

And I might try famotidine in half dose for a couple of days, since my gut has gotten bloaty feelings lately too (not that bad). Has anyone had experiences like this? What have you done about your H1 antihistamine, if anything?
 
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MCASMike

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I found this:

QUOTE: Anaphylaxis may be described as an overwhelming allergic reaction, typically involving multiple systems in the body, and representing a true medical emergency. It may be caused by a number of factors, but typically occurs in response to a foreign protein, which could be a food, drug, or other external allergen. Histamine, which is contained in mast cells throughout the body, may be released in massive amounts to create or to produce the symptoms and signs found with acute anaphylaxis. The largest concentration of mast cells exists in the skin, the lungs, and the gastrointestinal tract; but mast cells also exist in smaller amounts in other areas of the body. In response to contact with what could be extremely small amounts of this allergenic protein, an escalating cascade of mast cell mediator release may ensue...

The release of histamine granules from mast cells throughout these various body systems produces a number of clinical findings. First, histamine may cause vasodilation, resulting in hypotension and, in some cases, shock. Second, it may affect the heart directly, and it appears that both H1 and H2 histamine receptors may play a role in the cardiovascular manifestations of acute anaphylaxis. These cardiac manifestations, in addition to hypotension, may include tachycardia or more serious ventricular arrhythmias as well. The tachycardia experienced in anaphylaxis may occur by direct stimulation of histamine on the heart, UNQUOTE.

https://www.medscape.com/viewarticle/439721
 

MCASMike

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And this may help explain what happened to me two days ago:

QUOTE: "Allergy researchers target nighttime 'clock gene' activation."

Oct 28, 2013
KOFU, YAMANASHI PREF. – Researchers from Yamanashi University’s faculty of medicine have found that severe allergic symptoms at night and in the morning may be caused by high activation of genes in the mast cells during those hours.

The research group led by Atsuhito Nakao, a professor in the department of immunology at Yamanashi University, said if the activation of genes can be controlled by medicine, it would help control when patients come down with asthma and hay fever symptoms.

According to their study, the genes, called “clock genes,” drive the daily rhythm by inducing vibration inside the mast cells.

The research group said mast cells, triggered by increased activation of genes during the night, raise the level of allergic reactions to allergens such as pollen or tick dust and reduce the level during the day.

Development of symptoms such as nasal congestion or sneezing results from a reaction of histamine, a chemical released from mast cells while undergoing a reaction to allergens accumulated in the body, the researchers said.

They hope their findings can improve medical treatment for allergy sufferers.

Traditionally, medicine only tried to alleviate the effects of histamine, which affects the mucosa and respiratory organs.

“If we are able to control the activation of clock genes, we can also reduce the amount of histamine,” stressed Nakao.

Meanwhile, Tomomi Akagi, secretary-general of Atopikko Chikyu-no-ko Network — a Tokyo-based nonprofit organization for patients suffering from atopic dermatitis — suggested the method may be helpful in asthma treatment.

“There are many children whose asthma symptoms worsen in the middle of the night, but there are only few hospitals where they can be treated at night,” she said. “If we manage (to regulate the gene activation) to evoke symptoms during the day, we will be also able to alleviate the anxiety (children in need of help feel).”

The paper was published online in the Journal of Allergy and Clinical Immunology. UNQUOTE

https://www.japantimes.co.jp/news/2...chers-target-nighttime-clock-gene-activation/