Your child may get a fever (high temperature), pain in their joints or a and rash up to 5 days after an injection of omalizumab. Contact your doctor if this happens. Children who are at risk of parasite infection (worms) may get an infection. Talk to your doctor if you are concerned. Your child may get general aches and pains in their arms and legs or other joints, feel dizzy or tired, or experience itching and skin rashes.