We all consume a paracetamol or any antipyretic tablet when we have cold or flu. And these tablets just reduce the body temperature. So my question is, when we have an infection and due to that infection we get fever, so unknowingly if we consume antipyretic tablets it will reduce the body temperature, so that means during that condition reduction of body temperature is harmful for our body as the infectious agent can make copies of it, as the body temperature is decreasing.
This is a controversial topic. I co-authored a paper that drew on this research to make conclusions about population-level effects. The only situations I can recall where antipyretics have been shown to be clinically beneficial is in severe cases where inflammation itself is causing neurological damage (e.g., acute brain injuries); results for e.g. infectious diseases are ambiguous. In our paper, we summarized previous research on the costs and benefits of fever suppression as follows (our summary may be slightly biased in the direction of "fever suppression is bad" ...)
Previous investigations of the effects of fever suppression have focused on the clinical benefits and costs to the individual [8,9]. The adaptive value of fever [10–13] is well known to immunologists; for example, Janeway's Immunobiology [14, p. 110] notes that ‘At higher temperatures, bacterial and viral replication is less efficient, whereas the adaptive immune response operates more efficiently’. Others argue that the adaptive value of fever arises instead from activation and coordination of the immune response . By contrast, a common view in the medical community, as expressed for example in Harrison's Principles of Internal Medicine, is that the ‘treatment of fever and its symptoms does no harm and does not slow the resolution of common viral and bacterial infections’ [15, p. 107] ...
References from this section:
- Mackowiak PA. 2000 Physiological rationale for suppression of fever. Clin. Infect. Dis. 31, S185–S189. (doi:10.1086/317511)
- Eyers S, Weatherall M, Shirtcliffe P, Perrin K, Beasley R. 2010 The effect on mortality of antipyretics in the treatment of influenza infection: systematic review and meta-analyis. J. R. Soc. Med. 103, 403–411. (doi:10.1258/jrsm.2010.090441)
- Kluger MJ. 1991 The adaptive value of fever. In Fever: basic mechanisms and management (ed. Mackowiak PA), pp. 105–124. New York, NY: Raven Press Ltd.
- Hasday JD, Fairchild KD, Shanholtz C. 2000 The role of fever in the infected host. Microbes Infect. 2, 1891–1904. (doi:10.1016/S1286-4579(00)01337-X)
- Blatteis CM. 2003 Fever: pathological or physiological, injurious or beneficial? J. Thermal Biol. 28, 1–13. (doi:10.1016/S0306-4565(02)00034-7)
- Simon HB. 2003 Hyperthermia, fever, and fever of undetermined origin. In Infectious diseases: the clinician‘s guide to diagnosis, treatment, and prevention. (ed. Dale DC). New York, NY: WebMD Professional Publishing.
- Murphy KM. 2011 Janeway‘s immunobiology, 8th edn. New York, NY: Garland Science.
- Dinarello CA, Porat R. 2008 In Harrison's principles of internal medicine (eds Fauci AS, Kasper DL, Longo DL, Braunwald E, Hauser SL, Jameson JL, Loscalzo J), 17th edn, p. 2958. New York, NY: McGraw-Hill.
Both @ashafix and @benbolker have given a pretty nice answer, I just wanted to add some more points to it. First of all, it wouldn't be correct to say that
these tablets just reduce the body temperature as in that case, intaking antipyretics would be the same as drinking a glass of cold water in fever which, generally, shows the same effect as you mention in the question.
Paracetamol does reduce body's temperature. Though its exact mechanism is unknown, a theory from here suggests that:
The COX family of enzymes are responsible for the metabolism of arachidonic acid to prostaglandin H2, an unstable molecule that is, in turn, converted to numerous other pro-inflammatory compounds. Classical anti-inflammatories such as the NSAIDs block this step. Only when appropriately oxidised is the COX enzyme highly active. Paracetamol reduces the oxidised form of the COX enzyme, preventing it from forming pro-inflammatory chemicals. This leads to a reduced amount of prostaglandin E2 in the CNS, thus lowering the hypothalamic set-point in the thermoregulatory centre.
But, it also does other jobs like this:
An article in Nature Communications from researchers in London, UK and Lund, Sweden in November 2011 has found a hint to the analgesic mechanism of paracetamol, being that the metabolites of paracetamol e.g. NAPQI, act on TRPA1-receptors in the spinal cord to suppress the signal transduction from the superficial layers of the dorsal horn, to alleviate pain.
This conclusion has been contested in a new hypothesis paper on how paracetamol might act. The author concedes that NAPQI is the active metabolite but that this reactive compound should react not only with the thiol in TRPA1 but also with any other suitably available nucleophile that it happens to encounter. It is suggested that thiol groups in cysteine proteases, e.g. the proteases that take part in the processing of procytokines, such as those generating IL-1β and IL-6, might be the targets giving rise to overall analgesic effects.
Coming back to your main point i.e. when paracetamol reduces the body temperature (which it does), how is it helpful for the body to fight infections. Refer to this answer:
So when your body begins to fight an infection you get a fever (which can make the environment uncomfortably hot/cold) and the tissues around your joints swell (which makes movement and relaxation uncomfortable). NSAIDs like Ibuprofen reduce those symptoms, making the duration of the infection more bearable. They do not reduce the length of the infection by any measure (and might increase it, though the research is not particularly conclusive), but can make the day go by better if you've used up all your sick days or have a child to take care of.
Basically, people take NSAIDs to reduce fevers for the same reason most take any over-the-counter pain medications. To make life a little easier in the meantime.
A direct answer is given here:
While quality research has been lacking, there's some evidence that shows reducing a fever actually hinders recovery from infections, the cause of most fevers in the community, Young says...Also, if you take paracetamol to lower a fever, it may make you feel better because it also acts as a painkiller. (Whether lowering a fever in itself makes you feel better isn't clear.)...But when you're critically ill, some evidence suggests treating a fever might make it less likely you'll survive.
According to this study paracetamol/acetaminophen does not have any effect on the influenza virus.
Regular paracetamol had no effect on viral shedding, temperature or clinical symptoms in patients with PCR‐confirmed influenza. There remains an insufficient evidence base for paracetamol use in influenza infection.
Your statement "And these tablets just reduce the body temperature." might be an oversimplification. The mechanism of action of paracetamol is still a mystery but it is an analgesic which explains its use during viral infections.