See: Acetaminophen (Panadol, Paracetamol, Calpol, Salzone, Tylenol)   Ibuprofen (Apsifen Brufen Cuprofen Fenbid Inoven Motrin Nurofen  Proflex)

Quotes
Researchers who analysed data on more than 200,000 children found strong links between their exposure to paracetamol as infants and the development of asthma, eczema and other allergies at age 6-7.
    Fever often develops during an infection. Although we generally think of fever as a bad thing, fever enhances the inflammatory response of the body, and certain components of the immune system work optimally at increased body temperature. Also fever helps to limit the growth of some germs that cannot grow well at higher temperatures.
    Suppressing fever with medicines like Calpol interferes with this essential mechanism.
    For children, fever can serve another important function. Our children are not born with mature immune systems and fever is one way of activating and 'educating' the immune system to respond when needed. Because of this, temperatures up to 39 C (102 F) don't usually provide sufficient grounds for action unless your child is prone to convulsions. [2009] Behind the Label: Calpol by Pat Thomas

"Could the increase in all forms of meningitis and other infectious disease complications and deaths be because for the last 40+ years, the first thing parents do at the slightest sign of temperature is push paracetamol?  I believe so."--Hilary Butler IS FEAR OF FEVER HURTING OUR CHILDREN? By Edda West  - VRAN Newsletter January-March, 2003

Treating fevers is dicing with more severe infection, and a greater likelihood of death, because fever is a key immune response to get the immune system working properly.  You mess with fever, and you mess with lots of things. It stands to reason. Do you need to know what the medical profession does not yet know about fever in its totality, to see that? Bringing Chickenpox to the Boil by Hilary Butler

"The Ministry of Health's advice regarding the use of paracetamol in children is unscientific and unsafe," says Ron Law, a risk and policy analyst.  There is no scientific evidence supporting the routine use of paracetamol to reduce fevers in children, and certainly not in fevers up to 39°C as recommended by the Ministry of Health. It has been known for over a decade that routine administration of antipyretics such as paracetamol may interfere with the clinical evaluation of patients with infections, such as meningitis, that their use may prolong infection and reduce the antibody response in mild disease [and presumably following vaccination], and increase morbidity and mortality in severe infection. There is also no scientific evidence that antipyretics prevent febrile convulsions... it's all part of medical folklore that the Ministry advice is based on. Advice on Paracetamol is Unscientific and Unsafe