Sinusitis is the inflammation of the air spaces called sinuses around the nose and opening into the nose. Not all sinuses have developed yet at the time of birth. The development of most of the sinuses lasts until around the age of 7-12, but this does not mean that sinusitis will not be seen in children. Sinusitis can also be seen in children. Especially cold and flu-like viral upper respiratory tract infections can turn into sinusitis, and conditions such as allergic rhinitis, reflux and adenoid enlargement in the child may predispose to the development of sinusitis.