A healthy immune system is responsible for keeping the body safe from foreign viruses and bacteria that attack the healthy cells in the body. In this manner, it plays a huge role in warding off any infections or diseases. However, some factors can weaken the immune system over time, including unhealthy lifestyle choices, environmental factors, and genetic factors. Thus, here are some signs and symptoms to look out for that indicate a weak immune system. Frequent illnesses This is a very common symptom in anyone with a poor immune system. One may catch colds easily, and the symptoms that usually go away in a week last for longer. These individuals are also susceptible to getting food poisoning easily, which may take more than a couple of days to get treated. There are some barrier responses from the immune system which usually helps keep illnesses in check, and this includes: Cough reflex, which helps in expelling any foreign object which suddenly causes irritation. Stomach acid, which helps in killing the microbes which can enter the body through the food and drinks consumed. Mucus production, which helps in trapping bacteria and any other small particles which can cause irritation or cause infection in the body.