Weather can bring on relapses for those suffering from heart diseases. Stepping out in huangmei tian (the plum rain season) from June 20 with its continuous dampness is a problem for many people. Apart from discomfort in the chest and poor appetite, many chronic diseases reappear, especially potentially risky heart diseases.

TCM suggests a nap at noon, light exercise and a plain diet to protect your heart.

The annoying continuous rain and high humidity from mid-June to early or mid-July is a characteristic of the region south of the Yangtze River. And as it happens to be the season when local plums turn yellow and mature, it is called huangmei tian, literally meaning yellow plum season.

High temperatures, frequent rain and high humidity are all typical of this season. Apart from encouraging the growth of mould and bacteria, the weather can also bring on relapses for those who suffer from eczema, rheumatism, hypertension, arthritis and several heart diseases.

It is said that people feel most comfortable in an environment of about 22 degrees Celsius and 60 percent relative humidity. But during the huangmei tian, the temperature in Shanghai usually stays around 30 degrees with relative humidity ranging from 80 percent to 85 percent.

It is difficult for the human body to eliminate the irksome heat and dampness. That's why people often feel uncomfortable and irritable over this period.

TCM explains it as a strong pathogenic heat and dampness in the universe, invading the human body and causing energy disorders. Chest discomfort, psychological depression, poor appetite, indigestion and some functional disturbances of vegetative nerve like rapid heart rates or rashes on the face may occur.

Humidity leads to high energy consumption, which makes people get tired easily, according to Dr Zhou Duan, director of the TCM Internal Medicine Department of Longhua Hospital attached to the Shanghai University of Traditional Chinese Medicine.

In this case, the body needs faster blood circulation to transfer needed nutrition and energy, which eventually burdens the heart. Patients who already have heart problems, have to be careful with relapses, while healthy people should also be cautious about placing extra burdens on the heart for long periods.