Today, March 22, is International Water Day. Water is the universal solvent and one of the fundamental elements responsible for the appearance of life on Earth. It is part of almost everything around us, including our own cells. But what if I told you that there are people who have allergies to water?
a rare allergy
Although it may seem impossible, there is a type of allergy known as chronic water-inducible urticaria . Its technical name is aquagenic urticaria , and it is considered a rare disease, since it affects less than 1 person in 2000. The symptoms of this allergy are typical of any urticaria: welts on the skin, itching, swelling and redness . Sometimes the appearance of blisters of variable size (between 1-3 millimeters) is accompanied. The symptoms appear between 20 and 30 minutes after coming into contact with the water and disappear within an hour. This reaction occurs with any type of water: tap, salt, river… And at any temperature.
The symptoms are located in specific areas of the skin, which are usually the trunk and arms. However, some patients may have a predisposition for a specific area. This type of urticaria is tremendously uncomfortable for those who suffer from it and represents a great deterioration in their quality of life, since some must reduce the number of times they shower per week or even change cities or countries if they live in a climate with high humidity in the air . Even if they have mild symptoms, these people cannot carry out activities that we consider as normal, such as swimming in the sea, in the pool or taking a simple bath.
What is its cause and how is it treated?
Aquagenic urticaria falls into a category of urticaria caused by physical stimuli. In this category we also find vibration or pressure urticaria, although they are different stimuli, it is considered that they all can present a similar mechanism. However, the exact cause of the reaction to water is currently unknown. Urticariologists who are experts in this urticaria continue to investigate the mechanism of action to find effective treatments, but they still have more questions than answers.
In many of these patients, drinking water is not a problem or causes any reaction, which seems to indicate that the problem must be something localized to the skin. In other types of allergies or skin diseases, gastrointestinal symptoms may appear, but this is not usually the case with water urticaria.
The diagnosis of this disease is usually made based on the patient’s clinical history, since once it appears, it repeats itself every time it comes into contact with water. In case of doubt, there is a diagnostic test known as water challenge, where the patient can immerse part or all of their body in water.
The treatment depends on the degree of severity of the symptoms and how they affect the patient in their day-to-day life. Some people can keep the disease under control if they reduce the number of showers during the week, avoid humid places and do not bathe in lakes, swimming pools or the sea. However, sometimes it is necessary to add a treatment to prevent or minimize the appearance of blisters. The standard treatment for this disease is similar to that for other hives and allergies: antihistamines. They can be taken orally according to what the patient needs to control symptoms and lead a normal day-to-day life. However, not all patients improve with this treatment and even if they do, it would mean having this treatment for life as long as the symptoms continue.
For this reason, there are several studies underway that try to find alternative or complementary treatments for this and other hives. One of the most promising candidates is xolair, a compound that is responsible for sequestering IgE antibodies from the blood and is used in other types of allergies. Although the cause of aquagenic urticaria is not clear, this treatment is effective in some patients who suffer from it, which would support the hypothesis that it is a classic allergy. In these patients, the antibodies detect the water and recognize it as a danger to the body, as occurs in pollen allergies.
Even if this were one of the possible mechanisms, we continue to wonder what leads the body to detect one of the fundamental elements of life as dangerous.
Rory et al. 2016. A case of aquagenic urticaria successfully treated with omalizumab. J Allergy Clin Immunol Pract. doi: 10.1016/j.jaip.2015.12.017Wassef et al. 2017. Aquagenic Urticaria: A Perplexing Physical Phenomenon. Acta Dermatovereol Croat. doi: PMID: 29252177.Maurer et al. 2018. How to Approach Chronic Inducible Urticaria. J Allergy Clin Immunol Pract. doi: 10.1016/j.jaip.2018.03.007.