What to do if my 4 month old has a fever?

When my baby gets fever... My mum will always ask me to boil hard boiled egg and rub it on baby's front chest and back chest (most important) and also body. To only do it without any fan blowing at baby, or in a closed room without much wind. This is because to let baby perspire. Alternatively, keep sponging baby. Don't forget about the armpits and inner tights. These 2 areas are where heat always trap, once these areas are cooler temperature will also be brought down. Alternatively, if possible you can also soak baby in a tub of water and slowly add ice into the tub. This helps a lot, and brings down the temperature really fast.