Is it safe to give my 4-year-old son triaminic to relieve his cough and fever?

Safe/maybe/recommended=no. Studies in the US have shown these products have little to offer kids under 6 and have been discouraged for more than a decade. At most they give you something to do, at worst, the kid decides to self medicate later & ends up in the ER with an overdose, which is why they quit recommending it.

OTC meds like Triaminic do not have significant benefits and certainly don’t help recovery. Fever is generally beneficial to fighting infection and requires no treatment in most cases. Using acetaminophen for comfort is reasonable. Infections happen and recovery takes only a few days. If the child is ill beyond five days seek medical care.

The underlying cause of the coughand fever should be determined. Lung infections have many causes, and a COVID 19 screening test is recommended. Discuss the use of saline nasal spray to reduce post nasal drip with your pediatrician. If there is distress or fever for more than two days, a visit to your pediatrician is indicated. Avoid cough preparations at this age, but the saline may help.

Over the counter cold & cough medications are not recommended at his age.They do not help the underlying cause and have side effects.For persistent fever (T over 101) if he is not feeling well,acetaminophen can be given,but the fever is not dangerous,just a sign that his body is fighting infection.Plenty of fluids,rest,saline drops in his nose may help. See his doctor if not improving or if worse.