Green Tea & Onion Help Fighting Allergy: 
Allergy is common in Hong Kong and the prevalence is increasing. It is estimated that about 25% of adults suffer from allergies. The percentage for children is even higher with an approximation 50%. Food allergy is one of the most common types with about 3 % adults and 8% children having this problem. The difference in the ratio may be attributed to the undeveloped digestive and immune system in children.

What is allergy?
Allergy is the reaction of the immune system to some normally harmless substance in the environment. These substances can be pollen, dust, mold, pet dander and food. Hypersensitivity may not necessarily happen after the first exposures to these allergens. It can happen after several exposures. When allergens get into the body, they activate the body defense to release some antibodies such as IgE. These antibodies then combine with the immune cells, especially the mast cells and basophils, which would stimulate the release of histamine.

Histamine is a chemical substance that can cause vasodilation and smooth muscle contraction, resulting in allergic symptoms. The severity of allergic symptoms varies individually, but in general symptoms include rashes, shortness of breath, vomiting, sneezing and itchy eyes. For serious cases, it can cause coma or narrowing of the airways, which is fatal.  To avoid allergy, the best prevention is not to be in contact with any allergen. When contact is unavoidable, taking medication could be one way to control the symptoms. However, this type of antagonistic drugs are often associated with side effects such as dizziness, dry mouth, anxiety and insomnia.

On the other hand, many nutrients, including catechins, EGCG, polyphenols and quercetin, have the same beneficial effects as those antagonistic medications. In addition, these nutrients also boost immunity. Quercetin: Quercetin is a type of bioflavonoid with powerful antioxidative effect. It can be found in onion, raspberries and red grapes. Quercetin can stabilize the mast cells and basophils, thus preventing the release of histamine and alleviate the allergic response. Quercetin has anti-inflammatory property which can further relieve the allergic symptoms. Since quercetin can increase the absorption of vitamin C, it also helps keep the cells healthy.

Quercetin

Quercetin is a type of bioflavonoid with powerful antioxidative effect. It can be found in onion, raspberries and red grapes. Quercetin can stabilize the mast cells and basophils, thus preventing the release of histamine and alleviate the allergic response. Besides, quercetin has anti-inflammatory property which can further relieve the allergic symptoms. Since quercetin can increase the absorption of vitamin C, it also helps keep the cells healthy.  

Catechins and EGCG

Tea contains bioactive antioxidative substances: Catechins, EGCG and polyphenols. In addition to boosting immunity, clinical studies show that catechins and EGCG can block the IgE receptor, so it can prevent the release of histamine and alleviate allergic symptoms.

The concentration of catechins is depended on the degree of fermentation. The longer a tea is fermented, the lower its catechins content is. Since green tea doesn’t undergo fermentation process, it has the highest catechins content, which is 32-42% of dry weight. On the other hand, black tea undergoes full fermentation, so it only contains 8-10% catechins. Therefore, green tea is a better source of catechins than other types of tea. 

Healthy Tips

To avoid the air-borne allergens such as pollen, dust and molds, please

1.)    Stay indoors if possible, especially during the pollen season (e.g. early spring and end of autumn). Keeping the windows close, staying in air-conditioned room or using an air purifier are other options.

2.)    Keep the house clean  

3.)    Keep the pet out of the bedroom 

4.)    Keep the indoor humidity low

5.)    Wash the bed linens with hot water frequently to kill mites. 

For managing food allergy, it is important to avoid the food sources if possible, but also be caution with cross reactivity. For example, people who are allergic to cow milk may also experience the same hypersensitive reaction with goat milk or soy milk. Therefore, to avoid this happen, here are some suggestions;

1.)    Avoid eating food with unknown ingredients

2.)    Read the food label and ingredient list carefully

3.)    Be vigilant about verifying ingredients and preparation methods when dine-out

4.)    Never try to use the allergy-causing food when cooking at home