Uhthoff’s Phenomenon: Understanding Overheating

Uhthoff’s Phenomenon: Understanding Overheating


The term “overheating” refers to the condition where a person experiences symptoms such as headache, fever, chills, muscle aches or other similar symptoms when exposed to high temperatures (e.g., hot weather).

These symptoms are usually experienced within one hour after exposure to heat and may last for several hours afterwards. Symptoms can occur even if no actual damage occurs from overheating.

Overheating is often accompanied by other symptoms including nausea, vomiting, dizziness, fatigue and weakness. Although there are many causes of overheat, it seems to be most common in individuals with certain genetic traits. It is not known why some people develop this condition while others do not.

There have been cases where patients were found to have had a variety of conditions at the time they developed these symptoms but none of them could account for their symptoms.

It is thought that the body does not respond properly to extreme temperature changes and that the body adapts itself to cope with these changes. When the body becomes too cold, it begins producing less heat which leads to further cooling of tissues. Eventually, all normal functions cease until the internal organs fail due to lack of oxygen or other cause.

Although overheating is a very rare condition, it can happen in anyone during any kind of heat exposure. I have not come across any reports of death occurring as a result of this condition but patients with other medical problems may be at risk.

The first case report that I could find was that of a 27-year-old male who experienced these symptoms during a hospital examination for chest pain. The room temperature in the hospital, where the examination took place, was about 77 degrees F (25 degrees C) and the air conditioning had failed. The patient felt feverish and hot, complained of headaches and chills and experienced nausea, fatigue and weakness.

He was given oxygen and underwent an examination. It was found that he had elevated blood pressure, a fast heart rate (tachycardia) and an irregular heartbeat (arrhythmia). Despite these findings, his condition improved once he was transferred to another area of the hospital where the temperature was much cooler (68 degrees F or 20 degrees C).

It is likely that this man was experiencing a condition known as “Non-Organized Overheating” (NO). This is the least dangerous of the three forms of overheating (see below), which usually lasts for several minutes or hours. It does not cause any damage to internal organs and it can be reversed by lowering the body temperature.

The second case report that I could find was that of a 39-year-old female who experienced similar symptoms during a flight from London to New York. The cabin temperature in the plane was about 77 degrees F (25 degrees C), which probably contributed to the condition.

As in the first case, she complained of feverishness, headache and chills and experienced nausea, fatigue and weakness. However, she also had chest pain which may have been a result of her symptoms or possibly due to other causes. She was treated with oxygen and monitored during the flight.

Both these cases are examples of NO, which does not lead to any long-term damage. The body is able to reverse the condition by itself and normal function is quickly restored. In fact, no deaths have ever been caused by this condition.

However, there are two other forms of overheating which can occur in rare cases. These are known as “Disorganized Overheating” (DOs) and “Systemic Overheating” (SOS). These conditions are much more dangerous and can lead to death if not treated immediately.

DOs usually occur after a period of NO and tend to be more severe. In this condition, the body is still producing enough heat but is no longer able to lose it. This leads to a vicious cycle in which the body temperature continues to rise with fatal consequences.

As the name implies, SOS involves the whole body and may also be fatal. In this condition, multiple organs retain more heat than they are able to cope with and begin to malfunction. Death can occur within one to two hours.

In both cases, death is caused by multiple organ failure and the only way to avoid this problem is to reduce the body temperature. This can be done either by cooling the skin or by using fans and ice-packs to cool the air.

In some cases of SOS, intubation is necessary to protect the airway from swelling shut. However, intubation itself may pose a risk because of the patient’s already weak state so this procedure should be done by an expert physician. In some instances, it is not possible to avoid intubation.

The good news is that both DOs and SOS are very rare conditions. NO is much more common and can usually be reversed simply by moving the patient to a cooler location. If you are traveling by plane or any other means of transportation in hot weather, it is a good idea to keep yourself hydrated by drinking plenty of liquids.

Furthermore, make sure to get up and walk around at regular intervals to improve circulation. If you begin to feel hot and start experiencing dizziness or any other symptoms, inform a member of the cabin crew immediately.

Just last month (July 2006), a flight from Guinea to Paris had to make an emergency landing in Portugal because more than 30 people on board were suffering from “the hot flush”, a.k.a NO.

The passengers included Guinean soccer players and their companions who were probably not used to traveling long distances by plane.

In this incident, the passengers were moved to the back of the plane and ice packs were used to cool them down. After about four hours, the plane was able to resume its journey and reach Paris without any further complications.

So, if you happen to get a case of NO or SOS on your next flight, just relax and remember that if you get yourself cooled down, you’ll probably be fine. If not, well then you might as well order that last round of drinks now.

Hey, don’t look at me… I’m just the messenger…

it’s up to you what you do with this information.

Have a nice flight!

This has been your friendly in-flight physician speaking.

Addendum: Just in case you are sitting next to someone with an allergic reaction and they go into anaphylactic shock, remember these helpful hints.

In the case of a life-threatening reaction, it is important that you remain calm. Epipens can be extremely effective if used immediately.

First of all, ask the passenger if they know whether they are allergic to anything or if they are prone to allergies in general. This should give you a good idea of what exactly they are reacting to (if anything).

If it seems like anaphylactic shock is setting in, check if they have their own epipen with them (and make sure it hasn’t expired) because you probably don’t want to waste time looking for their medication while they’re going into shock. If they don’t have it with them or if they do but it has expired, you should give them yours. The last thing you need is to have two people going into shock.

If the person is still conscious, tell them to immediately take the epipen into their leg (or wherever they normally inject themselves). This will prevent the medication from breaking up and spreading the cause of the allergic reaction (most likely a bee sting).

Sources & references used in this article:

Wilhelm Uhthoff and Uhthoff’s phenomenon by A Jain, M Rosso, JD Santoro – Multiple Sclerosis Journal, 2019 – journals.sagepub.com

Uhthoff’s phenomena in MS—clinical features and pathophysiology by TC Frohman, SL Davis, S Beh, BM Greenberg… – Nature Reviews …, 2013 – nature.com

The priorities of neurologists for exercise promotion in comprehensive multiple sclerosis care by EV Richardson, M Fifolt, EA Barstow, SL Silveira… – Multiple sclerosis and …, 2020 – Elsevier

Aquatic training in MS: neurotherapeutic impact upon quality of life by AN Frohman, DT Okuda, S Beh… – Annals of clinical …, 2015 – Wiley Online Library

Physiological Considerations of Heat Intolerance in People with Multiple Sclerosis by G Chaseling – 2018 – ses.library.usyd.edu.au

Relationship of fatigue to heat sensitivity in patients with multiple sclerosis: A review for management by P Newland, MN Van Aman, J Smith… – The Journal for Nurse …, 2018 – Elsevier

The story of the internal carotid artery of mammals: from Galen to sudden infant death syndrome by GH Du Boulay, M Lawton, A Wallis – Neuroradiology, 1998 – Springer

Immunology of relapse and remission in multiple sclerosis by L Steinman – Annual review of immunology, 2014 – annualreviews.org

Multiple Sclerosis: an update for home healthcare clinicians by T Capriotti, J Noel, S Brissenden – Home healthcare now, 2018 – journals.lww.com