Two possible explanations: Firstly, symptoms of allergy like blocked nose , etc interfere with sleep;lack of good sleep can cause fatigue. Secondly, the allergic reaction leads to release of chemical mediators that induce fatigue. 

There are a couple reasons for the fatigue experienced when one has an allergic response. The first is because asthma and allergy affects your respiration and overall breaking. This can prevent you from having a good nights rest, leaving you fatigued throughout the day. Also, when your nose is stuffy, your tongue can fall backwards into your throat at nights as your try to sleep, creating a vacuum in the your throat leading to frequent waking spells throughout the night.

The second reason might be medication. While most of the newer allergy meds do  not lead lead to drowsiness, there are some that have drowsiness as a side effect.

I think the question is a real one as most clinicians would be asked by the patients, especially during the allergy seasons. The gentlemen above both offered the reasonable answers.

My take are:

First, the active immunological reactions in the host that resulted in the release of whole host of mediators. Those interleukins or cytokines are known to cause fatigue, especially interferon, IL-1, IL-6 and TNF.

Second, the quality of sleep suffered. Patients might toss around whole night without getting proper rest. They could hardly got into the state of deep sleep that relieve most of fatigue.

Third, we could not rule out what the drugs, especially of anti-histamine or decongestant(s) that might disturb sleep as well as causing drowsiness while trying to stay awake.

SWH

I would fully endorse Shih-Wen's statements (all 3 points!).

With regard to the interleukins I would add that immune-response modifiers such as imiquimod may cause interleukin release. And in fact, imiquimod may cause some fatigue, most likely via the interleukin release.

We should assume that allergy also is correlated to release of interleukins, Hence....

(But do not miss the other 3 aspects)

Dear, Ogail Dawod

I hope that you and your family are at ease. About this question, as you know that asthma & allergy conditions being approved as an action of immune reaction response which is tightly manifested by inflammatory immune response or (a complex immune reaction in such cases).That's, finally (accordance to type of immune stimulus) leads to promote synthesis, production, and releases to such of inflammatory immune mediators like; interleukins & cytokines which are mostly clarified by eosinophils, histamine present, as well as, to IL-1, IL-10,IL-4, IL-5 and TNF. Besides, not be forget that these types of reactions always during processing time were accompanied with increased of body temperature or ( fever ) and it's mechanisms effects in presence of fatigue. Meanwhile, the above factors were a concomitant with uncomfortable sleep and breath due to permeable vascular membrane changes that may result in congestion or (stuffy) nostril and narrowing bronchioles passages (bronchail-spasm action), that cause difficulty breathing, in addition to that factor you previously mentioned as allergy play an important role in way or another to disturb electrolytes balance. Therefor, all of these complicated outcome reflexes may acts as an a combination factors that were in final lead to develop and produce of fatigue during allergies conditions.

Yours Faithfully,

NASEER ALMUKHTAR 

Spring Allergy Cures: How Water & Electrolytes Prevent Allergy Symptoms

For people suffering from allergies, spring can be a dreaded time of year. There’s more pollen in the air, and of course, that can trigger those pesky allergy symptoms – runny nose, watery eyes, coughing, sneezing and sniffling.

Many people turn to over-the-counter antihistamines for relief. But they don’t always work, and their use is often accompanied by unwanted side-effects like drowsiness, dry mouth and slowed reaction time.

Luckily, there might be a simpler solution for seasonal allergies, and it’s as easy and affordable as water fortified with electrolytes.

Really? How Does Water Relieve Pollen Allergies?

Dehydration has many adverse effects on the body. During allergy season, not being properly hydrated may lead to more frequent and more intense allergy symptoms.  That’s right: If you’re body doesn’t have enough water, your sneezing, coughing and runny nose could be worse.

Here’s why this happens.

First, some studies suggest a lack of water causes you to produce more histamine, a protein that regulates water in the body and stimulates your thirst response. Histamine also plays a role in the body’s response to pollen. When you breathe in pollen, your body releases histamine, which is a main cause of allergy symptoms.

So if you’re thirsty, there’s more histamine in your body to be released, and thus, your symptoms may be stronger and last longer.

Secondly, a 2013 study found that dehydrated individuals produced less allergy-blocking antibodies.  With less of these antibodies, your body releases more histamine. Both of these contribute to more frequent and more intense allergy outbursts.

Why Should I Add Electrolytes?

Drinking an electrolyte-fortified beverage – like Drip Drop – helps the body retain fluids, which can help regulate the body’s histamine levels. Not to mention, the symptoms of allergies, especially during severe bouts, contribute to a greater loss of electrolytes, which you then need to replace.

Further, studies suggest that sodium –which is the most prevalent electrolyte in Drip Drop — has many uses as a natural antihistamine and anti-inflammatory. Preventing allergies isn’t just about staying hydrated; you need to replace electrolytes as well.

https://dripdrop.com/spring-allergy-cures-water-electrolytes-prevent-allergy-symptoms/

 dipeptidyl peptidase-4 (DPP IV, CD26) inhibitor indicated for treatment of Type II diabetes as a second line therapy after metformin. intolerant patients who developed anterior and posterior rhinorrhea, cough, dyspnea, allergy and fatigue deu to my contact with metformin patients used and abusal use for other treatment. 

While not disagreeing with any of the above, I'd like to add an observation. One interesting and unexplained aspect of a major anaphylactic reaction, reported by many patients who survive the experience, is a feeling of dread just beforehand: a terrible fear of something unknown, as in a nightmare. Which suggests - perhaps - that the mediators released during an allergic reaction of a less severe nature might also have some direct psychological effects.

That is a good observation. Most patients who experienced anaphylactic reaction had an aura of "feeling of doom". In those situations, the massive release of histamine and platelet activating factor (PAF) might have contributed to that feeling. As you know, if they survived, they went through the two most disastrous events, hypotension to shock and the severe form of bronchoconstriction, and the rush of stress hormone like cortisone trying to help reverse the process. 

Shih-Wen Huang

Thank you for confirming that observation. It would be interesting to know if people who suffered histamine poisoning (for example from eating tuna that has deteriorated due to poor storage) have that aura. If 'yes' then it may be just the huge dose of histamine. 

Linda,

You bring up interesting point. In fact, several years back, I had a case like that. The patient actually is a surgeon. He had scheduled a noon surgery. At the haste, he grabbed a piece of tuna steak sandwich from cafeteria and munched it before he scrubbed his arms and hands. Then, he went on to operating table.

After cleaning up patient's abdomen, he suddenly felt weak and ill. His colleagues soon noticed he had flushed face. After blurted out he was sick and weak, he passed out by the table. He was rushed to ER. His vital was not that bad, but he felt very weak. He also vomited all the ingested. After he recovered, he came to see me. His skin test and RAST vs. tuna were all negative. I then felt he had a food poisoning and patient fully agreed. He felt the sandwich was bad. Later, he did sample tuna sushi at home. He was O.K. He was elated. I believe that was the example of what you stated, ingestion of too much histamine from the spoiled fish.

Shih-Wen Huang,MD