You have mentioned about two issues - polyps and allergic rhinitis.
As regards nasal polyp, it will depend on what kind of Nasal polyp do you have. If it's non bleeding polyp and smaller in size, then Neti can help. You may start with Jala neti for few weeks. Thereafter you can go for sutra-neti, if it is possible. Alternatively, you can also try catheter neti, if sutra neti does not help. If you get good results, you may go ahead with cotton sutra. You should have to do neti regularly to have good results. However, we suggest that you must consult your physician to get your nasal polyp diagnosed before you practice neti.
The same jala neti/sutra neti would be helpful for allergic rhinitis which has the symptoms of watery, nasal discharge, sneezing, itching of eyes and increased eosinophil in blood. Jala neti and sutraneti help to clear the nasal secretions and opening the nasal passages. In addition, you can also use nature cure protocols under guidance of qualified nature cure practitioner which suggests cleansing of the internal system with a short fasts alongwith warm water enemas early in the morning to improve the immunity of the body. Under nature cure protocols, one can also use hot foot bath which helps relieving of congestion in the head region, heaviness in the head and other symptoms of cold. Steam/sauna bath also helps which helps in elimination of toxins from the body.
To prevent frequent attacks of cold/rhinitis, as well as to improve your resistance, you can also take adequate quantities of vitamin C through citrus fruit juices, amla and guava. For this, you may also consult with your physician.