We know the importance of staying hydrated, especially in hot weather. But even for something as simple as a drink of water, conflicting advice and urban myths abound.

Is cold water really bad for your health? What about hot water from the tap? And what is “raw water”? Let’s dive in and find out.

Myth 1: Cold water is bad for you

Some recent TikToks have suggested cold water causes health problems by somehow “contracting blood vessels” and “restricting digestion”. There is little evidence for this.

While a 2001 study found 51 out of 669 women tested (7.6%) got a headache after drinking cold water, most of them already suffered from migraines and the work hasn’t been repeated since.

Cold drinks were shown to cause discomfort in people with achalasia (a rare swallowing disorder) in 2012 but the study only had 12 participants.

For most people, the temperature you drink your water is down to personal preference and circumstances. Cold water after exercise in summer or hot water to relax in winter won’t make any difference to your overall health.

Myth 2: You shouldn’t drink hot tap water

This belief has a grain of scientific truth behind it. Hot water is generally a better solvent than cold water, so may dissolve metals and minerals from pipes better. Hot water is also often stored in tanks and may be heated and cooled many times. Bacteria and other disease-causing microorganisms tend to grow better in warm water and can build up over time.

It’s better to fill your cup from the cold tap and get hot water for drinks from the kettle.

Myth 3: Bottled water is better

While bottled water might be safer in certain parts of the world due to pollution of source water, there is no real advantage to drinking bottled water in Australia and similar countries.

According to University of Queensland researchers, bottled water is not safer than tap water. It may even be tap water. Most people can’t tell the difference either. Bottled water usually costs (substantially) more than turning on the tap and is worse for the environment.

What about lead in tap water? This problem hit the headlines after a public health emergency in Flint, Michigan, in the United States. But Flint used lead pipes with a corrosion inhibitor (in this case orthophosphate) to keep lead from dissolving. Then the city switched water sources to one without a corrosion inhibitor. Lead levels rose and a public emergency was declared.

Fortunately, lead pipes haven’t been used in Australia since the 1930s. While lead might be present in some old plumbing products, it is unlikely to cause problems.

Myth 4: Raw water is naturally healthier

Some people bypass bottled and tap water, going straight to the source.

The “raw water” trend emerged a few years ago, encouraging people to drink from rivers, streams and lakes. There is even a website to help you find a local source.

Supporters say our ancestors drank spring water, so we should, too. However, our ancestors also often died from dysentery and cholera and their life expectancy was low.

While it is true even highly treated drinking water can contain low levels of things like microplastics, unless you live somewhere very remote, the risks of drinking untreated water are far higher as it is more likely to contain pollutants from the surrounding area.

Myth 5: It’s OK to drink directly from hoses

Tempting as it may be, it’s probably best not to drink from the hose when watering the plants. Water might have sat in there, in the warm sun for weeks or more potentially leading to bacterial buildup.

Similarly, while drinking water fountains are generally perfectly safe to use, they can contain a variety of bacteria. It’s useful (though not essential) to run them for a few seconds before you start to drink so as to get fresh water through the system rather than what might have been sat there for a while.

We are fortunate to be able to take safe drinking water for granted. Billions of people around the world are not so lucky.

So whether you like it hot or cold, or somewhere in between, feel free to enjoy a glass of water this summer.

Just don’t drink it from the hose.

Oliver A.H. Jones, Professor of chemistry, RMIT University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

If you didn’t have food allergies as a child, is it possible to develop them as an adult? The short answer is yes. But the reasons why are much more complicated.

Preschoolers are about four times more likely to have a food allergy than adults and are more likely to grow out of it as they get older.

It’s hard to get accurate figures on adult food allergy prevalence. The Australian National Allergy Council reports one in 50 adults have food allergies. But a US survey suggested as many as one in ten adults were allergic to at least one food, with some developing allergies in adulthood.

What is a food allergy

Food allergies are immune reactions involving immunoglobulin E (IgE) – an antibody that’s central to triggering allergic responses. These are known as “IgE-mediated food allergies”.

Food allergy symptoms that are not mediated by IgE are usually delayed reactions and called food intolerances or hypersensitivity.

Food allergy symptoms can include hives, swelling, difficulty swallowing, vomiting, throat or chest tightening, trouble breathing, chest pain, rapid heart rate, dizziness, low blood pressure or anaphylaxis.

IgE-mediated food allergies can be life threatening, so all adults need an action management plan developed in consultation with their medical team.

Here are four IgE-mediated food allergies that can occur in adults – from relatively common ones to rare allergies you’ve probably never heard of.

1. Single food allergies

The most common IgE-mediated food allergies in adults in a US survey were to:

• shellfish (2.9%)
• cow’s milk (1.9%)
• peanut (1.8%)
• tree nuts (1.2%)
• fin fish (0.9%) like barramundi, snapper, salmon, cod and perch.

In these adults, about 45% reported reacting to multiple foods.

This compares to most common childhood food allergies: cow’s milk, egg, peanut and soy.

Overall, adult food allergy prevalence appears to be increasing. Compared to older surveys published in 2003 and 2004, peanut allergy prevalence has increased about three-fold (from 0.6%), while tree nuts and fin fish roughly doubled (from 0.5% each), with shellfish similar (2.5%).

While new adult-onset food allergies are increasing, childhood-onset food allergies are also more likely to be retained into adulthood. Possible reasons for both include low vitamin D status, lack of immune system challenges due to being overly “clean”, heightened sensitisation due to allergen avoidance, and more frequent antibiotic use.

2. Tick-meat allergy

Tick-meat allergy, also called α-Gal syndrome or mammalian meat allergy, is an allergic reaction to galactose-alpha-1,3-galactose, or α-Gal for short.

Australian immunologists first reported links between α-Gal syndrome and tick bites in 2009, with cases also reported in the United States, Japan, Europe and South Africa. The US Centers for Disease Control estimates about 450,000 Americans could be affected.

The α-Gal contains a carbohydrate molecule that is bound to a protein molecule in mammals.

The IgE-mediated allergy is triggered after repeated bites from ticks or chigger mites that have bitten those mammals. When tick saliva crosses into your body through the bite, antibodies to α-Gal are produced.

When you subsequently eat foods that contain α-Gal, the allergy is triggered. These triggering foods include meat (lamb, beef, pork, rabbit, kangaroo), dairy products (yoghurt, cheese, ice-cream, cream), animal-origin gelatin added to gummy foods (jelly, lollies, marshmallow), prescription medications and over-the counter supplements containing gelatin (some antibiotics, vitamins and other supplements).

Tick-meat allergy reactions can be hard to recognise because they’re usually delayed, and they can be severe and include anaphylaxis. Allergy organisations produce management guidelines, so always discuss management with your doctor.

3. Fruit-pollen allergy

Fruit-pollen allergy, called pollen food allergy syndrome, is an IgE-mediated allergic reaction.

In susceptible adults, pollen in the air provokes the production of IgE antibodies to antigens in the pollen, but these antigens are similar to ones found in some fruits, vegetables and herbs. The problem is that eating those plants triggers an allergic reaction.

The most allergenic tree pollens are from birch, cypress, Japanese cedar, latex, grass, and ragweed. Their pollen can cross-react with fruit and vegetables, including kiwi, banana, mango, avocado, grapes, celery, carrot and potato, and some herbs such as caraway, coriander, fennel, pepper and paprika.

Fruit-pollen allergy is not common. Prevalence estimates are between 0.03% and 8% depending on the country, but it can be life-threatening. Reactions range from itching or tingling of lips, mouth, tongue and throat, called oral allergy syndrome, to mild hives, to anaphylaxis.

4. Food-dependent, exercise-induced food allergy

During heavy exercise, the stomach produces less acid than usual and gut permeability increases, meaning that small molecules in your gut are more likely to escape across the membrane into your blood. These include food molecules that trigger an IgE reaction.

If the person already has IgE antibodies to the foods eaten before exercise, then the risk of triggering food allergy reactions is increased. This allergy is called food-dependent exercise-induced allergy, with symptoms ranging from hives and swelling, to difficulty breathing and anaphylaxis.

Common trigger foods include wheat, seafood, meat, poultry, egg, milk, nuts, grapes, celery and other foods, which could have been eaten many hours before exercising.

To complicate things even further, allergic reactions can occur at lower levels of trigger-food exposure, and be more severe if the person is simultaneously taking non-steroidal inflammatory medications like aspirin, drinking alcohol or is sleep-deprived.

Food-dependent exercise-induced allergy is extremely rare. Surveys have estimated prevalence as between one to 17 cases per 1,000 people worldwide with the highest prevalence between the teenage years to age 35. Those affected often have other allergic conditions such as hay fever, asthma, allergic conjunctivitis and dermatitis.

Allergies are a growing burden

The burden on physical health, psychological health and health costs due to food allergy is increasing. In the US, this financial burden was estimated as $24 billion per year.

Adult food allergy needs to be taken seriously and those with severe symptoms should wear a medical information bracelet or chain and carry an adrenaline auto-injector pen. Concerningly, surveys suggest only about one in four adults with food allergy have an adrenaline pen.

If you have an IgE-mediated food allergy, discuss your management plan with your doctor. You can also find more information at Allergy and Anaphylaxis Australia.

Clare Collins, Laureate Professor in Nutrition and Dietetics, University of Newcastle

This article is republished from The Conversation under a Creative Commons license. Read the original article.