Dr Sarah Jarvis is the Clinical Director of the Patient Platform, an active medical writer, broadcaster, and the resident doctor for BBC Radio 2.
Whether it’s a heatwave in the UK or the regular climate of countries closer to the equator, hot weather can seriously affect your health. While anyone can suffer from heat exhaustion or heatstroke, some groups are especially vulnerable, particularly those with pre-existing medical conditions. Heat can worsen symptoms or even trigger flare-ups in many chronic illnesses.
Below, we explore the medical conditions most affected by hot weather - and how to manage them better.
Breathing Difficulties: Asthma and COPD
Some estimates suggest more than 1 in 8 people in the UK have been diagnosed with asthma, which is especially common in children. While some children grow out of it, at least 5.4 million people in the UK live with asthma today - around 1 million of them with severe asthma, marked by daily or near-daily symptoms despite treatment.
COPD (chronic obstructive pulmonary disease) is another common lung condition, primarily affecting older adults. It is often caused by smoking, though not always, and about 3 million people in the UK are thought to have COPD, although many are undiagnosed.
Hot Weather Can Worsen Both Conditions for Many Reasons
Higher pollen levels during hot weather can trigger breathing difficulties, especially for individuals with allergies or asthma, as pollen becomes more airborne and widespread.
Hot air may irritate or narrow the airways, leading to increased discomfort and difficulty breathing. This is particularly challenging for those already dealing with respiratory conditions.
Air pollution tends to be worse on hot days, especially in cities, where stagnant air traps pollutants like ozone and particulate matter, further aggravating symptoms. This problem is compounded by the growing frequency of wildfires, which release smoke and fine particles into the air, creating hazardous breathing conditions.
Thunderstorms, often associated with humid air, can break pollen into smaller particles, which then circulate into the air. These tiny particles can deeply penetrate the smaller airways in the lungs, leading to severe irritation and worsening respiratory issues.
What You Can Do
Use your inhalers as prescribed – especially in the heat, where symptoms can worsen. Make sure your inhaler is always within reach and double-check that it hasn’t expired.
Monitor your symptoms closely and act early if you notice any signs of worsening, such as increased shortness of breath or wheezing. Have an action plan ready and consult your doctor if needed.
Avoid going outside during peak heat or high pollen times, as these can trigger flare-ups. If you must go out, try to stick to cooler parts of the day, wear a mask if pollen levels are high, and stay hydrated.
Digestive Issues: IBD and Dehydration
You'll know how important hydration is if you've had a stomach bug. Diarrhoea and vomiting can cause dehydration, which in turn leads to symptoms like dizziness, headaches, and poor concentration. In more serious cases, it can even trigger acute kidney damage.
For people with inflammatory bowel disease (IBD) - including Crohn’s disease and ulcerative colitis, flare-ups often involve increased diarrhoea. In hot weather, the risk of dehydration is even greater.
What You Can Do:
Stay well hydrated, especially during flare-ups. Drinking plenty of water throughout the day helps maintain your body’s balance and supports overall health. Aim for at least 8 glasses of water daily or more if symptoms are severe.
Avoid alcohol and caffeine, which can worsen dehydration. These drinks function as diuretics, causing your body to lose more water, which can aggravate your condition and make recovery slower.
Monitor symptoms and seek medical advice if needed. Pay attention to any changes or worsening of symptoms, and don’t hesitate to consult a healthcare professional for guidance or treatment to manage your condition effectively.
READ MORE: Staying Hydrated Whilst on Holiday
Medications, Sweating, and Heat Regulation
Sweating is essential for regulating body temperature, but certain medications can disrupt this process, either by increasing or reducing sweat production. Both scenarios can lead to serious heat-related health risks.
Medications That Increase Sweating
Some medications can cause excessive sweating, heightening the risk of dehydration, heat exhaustion, and even kidney damage. These include:
- Antidepressants (e.g., SSRIs)
- Medications for Alzheimer’s and other dementias
- Strong opioid painkillers
Medications That Reduce Sweating
Other medications can suppress sweating, potentially preventing your body from cooling down properly. This increases the risk of heatstroke. Examples include:
- Anticholinergics (used for overactive bladder, Parkinson’s disease, and irregular heart rhythms)
- Carbonic anhydrase inhibitors (prescribed for glaucoma, altitude sickness, epilepsy, and heart failure)
- Tricyclic antidepressants (used to treat depression and chronic pain)
Understanding how medications impact your body’s ability to regulate heat is crucial for staying safe, especially in hot conditions. Always consult your healthcare provider if you have concerns about these effects.
What You Can Do
Speak to your doctor if you're concerned that your medication affects your ability to tolerate heat. Some medications can impact how your body regulates temperature, so it's important to discuss any potential side effects and get advice tailored to your health needs.
Stay cool indoors and avoid peak sun hours. Keep your home well-ventilated or use air conditioning if possible, and try to plan outdoor activities for the early morning or late evening when temperatures are cooler.
Increase water intake proactively during warm weather. Even if you don’t feel thirsty, drink water regularly to stay hydrated and help your body stay cool. Adding fruits with high water content, like watermelon or cucumber, can also help boost hydration.
Neurological Conditions and Heat Sensitivity
Multiple Sclerosis (MS)
MS affects the central nervous system, leading to a wide range of symptoms including fatigue, vision problems, pain, and muscle spasms. Even a small increase in body temperature can worsen symptoms - a phenomenon known as Uhthoff’s phenomenon.
Migraines
Roughly 6 million people in the UK experience migraines. Triggers include:
- Dehydration.
- Bright sunlight.
- Irregular meals.
- Stress or anxiety.
In hot weather, migraines can become more frequent and more intense.
Postural Tachycardia Syndrome (PoTS)
PoTS is a condition of the autonomic nervous system. Symptoms include:
- Light-headedness.
- Palpitations.
- Excessive sweating.
- Dizziness when standing.
- Poor sleep and fatigue.
PoTS is often linked to ME/CFS and autoimmune diseases like Lupus and Sjögren’s syndrome. In hot weather, issues with sweating and dehydration can significantly worsen symptoms.
Ehlers-Danlos Syndromes (EDS)
EDS affects the connective tissues in the body, including joints, skin, and blood vessels. Symptoms such as dizziness, migraines, palpitations, and heat rashes can all become more problematic in hot weather.
What You Can Do
- Rest in cool, shaded areas when needed.
- Use cooling aids like fans or cooling towels.
- Stay hydrated and manage triggers proactively.
Autoimmune Conditions and Sunlight Sensitivity
Autoimmune diseases like Lupus and rheumatoid arthritis occur when the immune system mistakenly attacks the body’s own tissues, causing symptoms such as fatigue, joint pain, and inflammation. These conditions can significantly impact quality of life, and managing triggers is a key part of reducing flare-ups.
One common trigger, particularly for those with Lupus, is sunlight and UV exposure. Even short periods of sun exposure can lead to increased inflammation, skin rashes, and worsening fatigue. This sensitivity happens because UV rays can alter skin cells, prompting an overactive immune response in individuals with autoimmune conditions.
What You Can Do
Avoid direct sunlight whenever possible, especially during peak UV hours between 10 a.m. and 4 p.m. Stay in shaded areas or indoors when the sun is strongest.
Wear protective clothing such as long-sleeved shirts, long pants, UV-blocking sunglasses, and a broad-brimmed hat to shield your skin and eyes.
Apply a high-factor sunscreen (SPF 30 or higher) to all exposed skin, even on cloudy days. Make sure to reapply every two hours, especially if you're sweating or swimming.
By taking these precautions, individuals with autoimmune conditions can better protect themselves from UV-related triggers and maintain greater control over their symptoms.
Skin Conditions and Light Sensitivity
Rosacea
Rosacea affects the skin of the face, leading to redness, spots, and thickened skin. Around 1 in 10 people in the UK are thought to have it. Sunlight, heat, and even spicy foods or alcohol can make rosacea worse.
Visual Impairments
People who are visually impaired may find hot weather challenging. For example:
Sunglasses can reduce essential light perception.
Wide-brimmed hats (used to block the sun) may interfere with echolocation, which some visually impaired people rely on for navigation.
What You Can Do
Consider using UV-protective clothing, visors, or sunglasses as an alternative to wide-brimmed hats if echolocation or spatial awareness becomes an issue. These options can provide effective sun protection without compromising your ability to navigate your surroundings.
Ensure your facial skin is well-protected by applying high-SPF sunscreen regularly and monitor any symptoms of rosacea carefully. If redness or irritation worsens, consult a dermatologist for tailored advice on managing the condition and protecting your skin.
Hot weather affects everyone, but for people with chronic or underlying medical conditions, the risks can be greater and more complex. From breathing difficulties to heat-sensitive neurological disorders, understanding the impact of temperature is key to managing your health.
Being proactive - by staying cool, staying hydrated, avoiding midday sun, and knowing how your medications or conditions interact with heat - can make a huge difference.