Winter is on the way, bringing colder and breezier days: an extra challenge for the immune system and a higher chance of catching a cold or the flu. When you start feeling feverish, the instinct is to reach for the medicine cabinet straight away. But a fever is not always the enemy: it is often the immune system working exactly as it should. Here is how to break a fever safely when you need to, and how to tell when it is better left to run its course.
Is a fever good, actually?
Most illness-causing microbes, bacteria and viruses alike, thrive at the body's normal temperature and replicate poorly once it rises. A fever spurs the immune system into action, and letting a mild one run its course may actually shorten a cold or flu, reduce its severity, and strengthen immunity against future infections. So yes, within limits, a fever is good: it is a sign the body is responding, not malfunctioning.
This view is gaining ground within the medical community, but the cause of the fever still matters, particularly in children, pregnant women, travellers and older adults. Where a dangerous condition can confidently be ruled out, the best approach is to manage the fever and keep it at a reasonable level, below 39°C, rather than eliminate it outright.
How does a fever help the immune system?
The febrile response is well known to accompany the fight against infection, and despite its considerable energetic cost, the body has kept it through evolution: a strong sign it plays an important role in stimulating immunity.
Studies have shown that higher temperatures alter the composition and fluidity of cell membranes, making it harder for pathogens to enter cells. Another study demonstrated a further mechanism: raised temperature alters the surface proteins on immune cells called lymphocytes, making it easier for them to travel through the body and reach sites of infection.
Feeling hot or feverish, but no fever?
Not every hot, flushed or achy feeling is a true fever. Anxiety, hormonal changes, hot flashes, dehydration, alcohol, spicy food, exercise and even a warm room can all make you feel feverish without raising your core temperature. A true fever is a measured one: normal body temperature sits around 36 to 37°C, and anything from about 38°C up counts as a fever. If you feel hot but no fever shows on the thermometer, the fix is usually simpler: cool the room, hydrate, and remove a layer, rather than treating for infection.
It is also common to feel feverish in the hours before a measurable fever develops, as the body's set point starts to rise. Taking your temperature again after 30 to 60 minutes usually settles which one you are dealing with.
How to break a fever safely
Take your temperature regularly with a thermometer, so you are managing a number, not just a feeling.
Drink plenty of fluids to prevent dehydration, which a fever makes more likely.
Dress lightly and keep the room cool rather than bundling up, which traps heat in.
Rest, and know when to stop pushing through the day. This matters enormously in today's hectic society: if you cannot find space in your life for wellness, you may eventually be forced to find space for illness.
Consider immune-boosting supplements such as vitamin C, zinc, echinacea and propolis.
If your temperature climbs higher than feels comfortable, try sweating it out first with yarrow (Achillea millefolium), one of the best herbs for fever. Yarrow is what herbalists call a cooling diaphoretic: it opens the pores and induces perspiration, which helps control and reduce body temperature while releasing toxins. Take it as a hot infusion: 1 to 2 teaspoons of dried yarrow in a cup of boiling water, steeped for 15 minutes, strained and drunk warm, three times daily, ideally while covered up in bed.
Over-the-counter options such as acetaminophen or ibuprofen can bring a fever down when it is making you genuinely uncomfortable, but using them just to chase a normal reading is usually unnecessary once the fever is mild and behaving as expected.
When to let a fever run its course, and when to get help
A mild fever, under about 39°C, in an otherwise healthy adult who is drinking fluids and resting, is usually safe to manage at home and let do its work. Letting it run is different from ignoring it: keep checking your temperature and how you feel.
Call a doctor or seek care if the fever climbs above 39.4 to 40°C, lasts more than three days, or comes with a stiff neck, confusion, a rash, difficulty breathing, persistent vomiting, or severe pain. Children, pregnant women, older adults and anyone with a chronic condition should have a lower threshold for checking in with a doctor rather than waiting it out.
That is how a fever can be your best friend, keeping infection at bay, right up until it needs a hand. Next time you feel a little hot, take your temperature before you take anything else: it tells you whether to let it run, help it along, or make the call.
References
Cited by the original article:
Lin CD, et al. Fever Promotes T Lymphocyte Trafficking via a Thermal Sensory Pathway Involving Heat Shock Protein 90 and α4 Integrins. Immunity (2019). doi:10.1016/j.immuni.2018.11.013
Mace TA, et al. Differentiation of CD8+ T cells into effector cells is enhanced by physiological range hyperthermia. J Leukoc Biol. (2011). doi:10.1189/jlb.0511229
Mills S, Bone K. Principles and Practice of Phytotherapy, Modern Herbal Medicine (2008). Churchill Livingstone.
Papatriantafyllou M. Heating up T cell activation. Nat Rev Immunol. (2012). doi:10.1038/nri3146
Plaza JJG, Hulak N, Zhumadilov Z, Akilzhanova A. Fever as an important resource for infectious diseases research. Intractable and Rare Diseases Research (2016). doi:10.5582/irdr.2016.01009
