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Allergic Oddities: The World's Rarest Allergies

Hold your pollen and peanuts! In the realm of allergies, some are known all too well, while others remain shrouded in rarity and mystery. These uncommon allergies can pose unique challenges for those affected, often requiring heightened awareness and understanding. In this blog post, we embark on a journey to explore some of the world's rarest allergies affecting only a fraction of the population.

A three-photo collage of a sunset, water, and a hand holding a 5 Lb weight.
Pexels | Towfiqu Barbhuiya

World's Rarest Allergies

1. Water Allergy

Imagine being allergic to water itself. Aquagenic urticaria (AU) is an extremely rare condition where contact with water, regardless of temperature, triggers hives, itching, and, in severe cases, anaphylaxis. A condition as fundamental as water allergy poses unique challenges in daily life. Since 2017, approximately 50 cases of AU have been documented in medical literature, with its initial descriptions dating back to 1964.

Hives usually develop within 30 minutes of water contact and last anywhere from 30 minutes to 2 hours before fading away on their own. While anyone can experience this, it's more common in females after puberty. Drinking water rarely triggers symptoms, but the mouth and lips might be affected.

A wet hand over a body of water. | ENT Family Blog: The World's Rarest Allergies.

2. Allergy to Vibrations

To this day, the prevalence of people with an allergy to vibrations, or vibratory urticaria (VU), is unknown. People with this rare disorder find that basic activities like running, clapping hands, towel drying, or even taking a bumpy bus ride can induce temporary skin rashes.

In 2016, a breakthrough for this rare condition was found. A family exhibiting VU symptoms was evaluated at the NIAID, led by co-author Dr. Hirsh Komarow. During the investigation, researchers uncovered a 1980s Yale study on another family with similar symptoms. The Yale researcher connected the NIH team with the second family, who, in turn, referred a third family sharing the same symptoms, all becoming part of the study.

The first family traced their roots to the Lebanese city of Zgharta. In the 1980s publication, it was mentioned that the second family also hailed from Zgharta. DNA fingerprinting revealed that the three families were interconnected, representing different branches of one big family network. A deeper dive revealed that all family members with symptoms shared a specific gene mutation in ADGRE2, a gene present in mast cells. This mutation, it seems, was the trigger for their unique histamine response to vibrations.

3. Sun Allergy

Sun allergy, also known as photosensitivity or sun poisoning, is a group of skin conditions that cause an abnormal reaction to sunlight exposure. It's not a true allergy in the classic sense, but rather an oversensitivity of the skin to ultraviolet (UV) rays from the sun.

There are several different types of sun allergies, each with its own set of symptoms and triggers. The most common type is polymorphic light eruption (PMLE), impacting up to 15% of the global population, with a higher prevalence among women. PMLE typically causes an itchy, red, bumpy rash to appear on sun-exposed skin within a few hours or days of exposure.

A type of sun allergy, polymorphic light eruption.
DermNetNZ, CC BY 4.0 <>, via Wikimedia Commons

According to Harvard Health Publishing, other types of sun allergies include:

  • Solar urticaria: This rare condition causes hives to develop within minutes of sun exposure.

  • Actinic prurigo: This chronic condition causes itchy, papular (small, bump-like) lesions to develop on sun-exposed skin.

  • Photoallergic reaction: This occurs when a topical medication or other substance reacts with sunlight to cause a rash.

The exact cause of sun allergies is unknown, but it's thought to be linked to an abnormal immune system response to UV rays. People with fair skin, a family history of sun sensitivity, or autoimmune diseases are more likely to develop sun allergies.

4. Exercise-Induced Anaphylaxis

Engaging in physical activity is typically associated with health benefits, but in rare cases, exercise induces allergic reactions, including anaphylaxis. Exercise-induced anaphylaxis is a rare disorder that causes an allergic reaction during physical activity.

This reaction can range from mild to severe and can start during any stage of physical activity. The symptoms of exercise-induced anaphylaxis can affect your skin, heart, and lungs. These symptoms include coughing, difficulty breathing, or wheezing, along with other symptoms such as flushing, generalized itchiness, facial swelling, hives, or feeling like your throat is closing. You could even experience gastrointestinal symptoms like an upset stomach, abdominal cramps, diarrhea, and vomiting

The exact cause for exercise-induced anaphylaxis isn’t exactly clear. However, it’s known that more vigorous exercises are usually blamed for exercise-induced anaphylaxis. In up to half of EIA cases, the culprit isn't exercise alone, but a specific food eaten beforehand. This is referred to as food-dependent exercise-induced anaphylaxis. Certain medications like aspirin and anti-inflammatories can trigger the reaction, as well as extreme temperatures, humidity, and hormonal changes

5. Cold Urticaria

Cold urticaria turns the ordinary act of exposure to cold temperatures into a potential allergic trigger. A meta-analysis conducted in 2022 determined that cold urticaria affects about 7.6% of people with chronic urticaria (CU) and 26.1% of people with chronic inducible urticaria (CIndU). This translates to roughly 6 out of every 10,000 people worldwide having cold urticaria at any given time. Hives, swelling, and itching can occur upon contact with cold air, water, or surfaces. They usually develop within minutes of exposure and can last for hours.

Some people with cold urticaria may also experience:

  • Burning or stinging sensation on the skin

  • Abdominal pain

  • Dizziness

  • Lightheadedness

In rare cases, severe reactions can even lead to anaphylaxis, a life-threatening allergic reaction requiring immediate medical attention. H1-antihistamines are the first-line treatment, but other options are available.


The world of allergies is vast and varied, with some being more common and others incredibly rare. These five allergies we’ve explored serve as a testament to the complexity and uniqueness of the human body. As we continue to delve into the mysteries of our immune system, we gain a deeper understanding of these rare conditions, paving the way for better treatments and management strategies.

For those facing these unique challenges, know that you are not alone. Community support groups and online forums provide a platform for sharing experiences, coping strategies, and emotional support. With every new study, we move a step closer to better understanding these allergies, improving treatments, and potentially finding cures. So as we move forward, stay curious, stay informed, and most importantly, stay healthy.


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Dr. David Eleff, Otolaryngologist/Ear, Nose, and Throat Specialist at ENT Family in Hollywood, Florida.

This article has been medically reviewed by  otolaryngologist, David Eleff, M.D.

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