Benylin day and night contains diphenhydramine, pseudoephedrine and paracetamol. Benylin day and night tablets help reduce temperature, relieve aches and pains, help clear congestion and so make it easier to nod off at night. Diphenhydramine helps to relieve a runny nose, whilst pseudoephedrine causes the blood vessels in the nasal and sinus passages to contract and narrow, reducing congestion and the production of excess mucus. Paracetamol helps bring down a fever and provide relief from headaches or bodily aches and pains.Benylin day and night should be avoided during pregnancy as it contains pseudoephedrine which in the first trimester may be associated with defective closure of the abdominal wall (gastroschisis) in the baby.