“You can’t make antibodies against the cold, so an allergy can’t develop”, explains allergist Markus Magerl of the Allergy Center Charité Berlin (ECARF 2017)
And yet some people develop a skin rash when they are exposed to low temperatures. When this happens, the skin looks and feels as if it had come into contact with stinging nettles. This is why the rash is called nettle rash, or urticaria.
There are various triggers that can cause urticaria. Only three per cent of these are allergy-related.
Urticaria is usually linked to other causes: In one in five people with urticaria, the condition is triggered by physical stimuli such as light, friction, vibration, pressure, and also cold (Wütherich 2006). Women appear to be twice as likely as men to experience cold urticaria. Symptoms usually do not occur until early adulthood.
Franziska Rueff, senior physician at the Clinic and Polyclinic of Dermatology and Allergology at Ludwig-Maximilians-Universität München, estimates that around 50,000 people in Germany have cold urticaria (BR Television, 2020).
Individual cold triggers
The temperature at which problems arise varies widely depending on the individual. There is no single threshold temperature. “Some people react when the skin is cooled down to four degrees Celsius, while others react as soon as the skin reaches 20 or even 30 degrees Celsius”, says Marcus Maurer, director of research at the Department of Dermatology at Charité Berlin.
Therefore, if cold urticaria is suspected, the threshold temperature for each patient must be individually determined – for example, by touching the skin with containers that are filled with liquids of different temperatures, or by immersing the arm in cold water.
The TempTest®, developed by Charité Berlin, is even easier. The device generates temperatures between 4 and 44 degrees Celsius. It can be used to quickly determine the threshold temperatures for cold and heat urticaria (Magerl, 2015).
However, it is important to know that cold urticaria often disappears on its own after five to seven years. The diagnosis should therefore be repeated every couple of years by running the tests on a regular basis.
How to treat cold urticaria
If cold urticaria is diagnosed, the lowest temperature to which the patient can be exposed is determined. The associated triggers should then be avoided:
- Do not consume or handle cold foods or drinks
- Dress warmly when it is cold outside, and do not forget to cover the face and hands
- Do not jump into cold water
These measures are usually sufficient to prevent symptoms.
If you still want to expose yourself to lower temperatures, as you would do when going for a cooling swim on a hot summer’s day, the latest European urticaria guideline (Zuberbier 2018) recommends that you take an antihistamine two hours before you jump in.
The best antihistamines for this are the second generation non-sedating H1 antihistamines, which do not cause drowsiness. The standard recommended dose is usually not effective for treating urticaria. According to the guideline, the dose may need to be increased by up to four times. However, the dose should not be increased arbitrarily. A doctor should be consulted for the correct antihistamine and dosage.
Rare but sometimes dangerous
“Cold urticaria is rare, but it has a strong impact”, says Maurer (Schuster, 2019). When large parts of the body are exposed to cold temperatures – for example, when jumping into cold water – the blood circulation of the organs can be restricted. If insufficient blood reaches the vital organs, such as the heart and brain, anaphylactic shock can be triggered in severe cases.
Another possible serious complication is the swelling of the oral mucosa and tongue, says Maurer. This can occur when cold food or drinks are consumed. In the worst case, the swelling will prevent air from reaching the lungs.
If you have already experienced life-threatening complications, you should be well equipped for the next emergency. Inform the people around you and obtain an emergency kit from your doctor that you can carry with you at all times.
Wütherich B et al. Physikalische Urtikaria: Klinik, Diagnostik und Therapie. Schweiz Med Forum. 2006;6:215-24. (Physical urticaria: clinical symptoms, diagnosis and therapy). Swiss Medical Forum. 2006;6:215-24 (in German).