Cancer is a major health problem worldwide (
1). Cancer deaths are expected to rise to 13 million worldwide by 2030. Cancer is the leading cause of death in developed countries and the second leading cause of death in developing countries (
2). In Iran, cancer is the third most common cause of death after cardiovascular diseases and vehicle accidents (
3). Colon cancer is one of the most common types of cancer and is the second most common cause of cancer death that affects both men and women in developed countries (
4). The incidence of colon cancer is high in many Asian countries and more profoundly in developed and western countries (
5). In 2010, it accounted for 10% of all cancer deaths in the United States, causing 50 to 60% of patients to experience metastases and more than 30% of patients with metastatic symptoms to refer to the hospital (
6).
One of the most important therapeutic options for cancer is chemotherapy that uses anti-cancer agents to kill tumor cells. Chemotherapy is the cornerstone of cancer treatment and, as a systematic treatment, kills cancer cells in the furthest parts of the body (
7). Several chemotherapy regimens are used to treat colon cancer, and the basis of all is 5-FU (5-fluorouracil), which is used as an effective drug in the first-line treatment for colon cancer. The main side effect of this drug in different regimens is bone marrow suppression, mucositis, and diarrhea (
8). Mouth flora in a healthy person remains constant over time; however, special conditions can cause mouth flora to collapse. For example, within 48 hours of the patient’s hospitalization, this flora changes in favor of gram-negative organisms with higher pathogenicity (
9). These changes can lead to the accumulation of bacteria and the proliferation of opportunistic pathogens in the oral cavity, causing general and local complications (
10), such as inflammation, mouth ulcers, increased prevalence of viral, fungal, and bacterial infections, and bleeding. These complications lead to significant pain and malnutrition (
11).
In patients needing intensive care, a defensive substance called fibronectin, commonly found on the surface of the teeth and mouth, deteriorates (
12), and develops mucositis as a significant complication (
13). The incidence of severe mucositis has been reported in more than 60% of patients receiving radiation therapy in the body as a whole and 30 to 50% of patients not receiving general radiotherapy (
14). The severity of mucositis varies in the mouth from small scars with redness to severe ulcers and ruptured mucous and epithelium. Severe mucositis can cause damage to the lining of the mouth, which impairs its function and can lead to morbidity and poor quality of life of patients (
15). Clinically, it can cause major problems, including many disabling symptoms, such as dysphagia, weight loss, and malnutrition during treatment (
16). The prevalence of mucositis is 80 to 100% in high-dose chemotherapy, 40% in standard-dose chemotherapy, and 10 to 15% in low-dose chemotherapy (
17). The only way to treat and prevent chemotherapy-induced mucositis is by observing oral hygiene and using mouthwash (
18). Due to complications such as burning, allergies, bitter and intolerable taste and exacerbation of mouth ulcers, non-chemical mouthwash is recommended to use, especially herbal mouthwash (
19).
Over the past few years, the use of complementary and alternative medicine has become popular (
20). One of the treatments in complementary medicine is the use of herbal medicine, which has received general public acceptance due to lower side effects (
21). One of these medicinal herbs is licorice, which is considered by pharmaceutical and food industries due to a large number of flavonoids (
22). The natural form of this substance is useful in the treatment of mouth and digestive tract ulcers (
23). A study conducted by Das et al. in 2011 found that licorice was effective in preventing and treating oral mucositis caused by radiotherapy in patients with cancer in the head and neck without any interruption in treatment (
24). According to these studies and the use of complementary medicine in mucositis by patients undergoing chemotherapy, licorice can be applied to reduce the complications of chemotherapy due to its prominent anti-inflammatory symptoms.