You have to understand that allergy to a certain allergen that
trigger your "blocked nose" in the first place happens throughout
your life (whenever you are exposed to it).
Steroidal medications (they are safe) are for symptomatic relief
(they treat the symptoms, they don't cure the disease). Hence once
you are relieved symptomatically, there is an inevitable return of
such symptoms once exposed to the things that you are allergic to.
The body has these cells known as mast cells that release
histamines in huge amount to trigger off such allergic symptoms.
The thing is that the antibody IgE (which is the key to opening the
door for the release of histamines by mast cells) is attached to
mast cells after the first exposure to such allergens. Such
attachment increases the rapidity of histamine release because they
are already attached to the lock. What it needs is an allergen to
sit on top of them (ref IgE) and turn them to open the door. Hence
the analogy is that the mast cells are the door that contains
histamine in the inside, the IgE is the key and the allergens are
the hands that turn the key to open the door. (Note that none of
the medications used can remove these IgE, antihistamines work by
inhibiting the histamine chemical's effects on the receptors.
Histamines once released will find their receptors and sit on them
leading to allergic symptoms. Your loratidine works in such a way
that it sits on these receptors first, but the magic is that they
do not cause an effect. The histamines in the body would then be
unable to sit on the receptors for they have been occupied.
Steroids on the other hand works by easing up the bronchial
muscles, reducing the inflammation and clearing the inflammatory
chemicals from the site of the allergy, hence helping to reduce the
symptoms).
The best way or the first line treatment is to avoid the things
that you are allergic to. Remove your carpet if you have one in
your bedroom or your house, keep your curtains clean (wash them
weekly), reduce the number of pillows (hence the covering) or
mattresses in your room, if you have pets and if you are allergic
to their danders, its time to consider letting them out rather than
in the house (if they are house pets), etc.
The severity of your blocked nose dictates the course and
frequency of medication you will be put on. Your's is a
type of allergy known as perrenial allergic rhinitis (happening
throughout the year when exposed to certain chemicals or dust that
you are allergic to). There is another one known as seasonal
allergic rhinitis (but this happens more often in countries that
have four seasons, and their blocked and irritatations of the nose
comes only in particularly one specific season repeated annually).
As yours is yearly, you would often face these symptoms
frequently.
Heed your ENT specialist advice on your medications intake and you
will be fine.