There are several natural methods that can be tried.
First the non-pharmacological methods

1. First thing in the morning, before eating or drinking anything, make it a practice to GENTLY brush the very back of the tongue with a soft tooth brush [ as far back as you can go]. This will make you retch and try to vomit. You will very likely bring up significant amounts of mucus which you should spit out. Your eyes will water just like when you vomit and your stomach will dry heave [ as it is empty]. Your tooth brush bristles will have a coating of mucus on it which you will want to wash off before you repeat each time. Do this initially just two or three times every morning and in a week you should be able to do it quite easily. If you have any stomach issues such as reflux or acidity please check with your doctor first since the retching might cause some aggravation.
2. The ear allergy point..see pic and video link. These points should be massaged gently but firmly between the thumb and fingertip [make sure your nails are clipped, filed properly and are not sure sharp and do not injure the skin in anyway]. If you are able to use the seeds that is ideal.
3. Begin a practice of Pranayama, most importantly the practice of alternate nostril breathing. Initially this will be difficult especially if there has been chronic nasal congestion and the development of polyps in the nose. If you persist and go slowly but steadily this practice alone could solve your problem but it would be even better to combine it with a full yoga practice that you could engage in as a family. Best to find a good yoga teacher or attend a proper course.
4. Diet is important of course but elimination diets for allergies need to be supervised and supplemented as needed especially in children so I would suggest finding someone locally who can help you with that.
   I am not sure what is available to you in Venezuela in terms of Schuesslers salts and Homoeopathy, but those would be the next choice in therapy. A good Schuessler salt combination for hayfever is MagPhos 6x, Nat mur 6x, Silica 6x one tab 3 times a day. Homoeopathy would ideally involve a proper consult with a good homoeopathic physician. Remedies such as Dulcamara or others depending on your symptom profile can be very useful. There are other types of natural remedies too including herbs. I however always recommend trying the simple non-pharmacological self-help techniques described above first before progressing to any medication. I have had several clients respond dramatically but they did take the time and effort to do this.