Chemo-induced mucositis is a common complication in patients treated for hematologic malignancies. They can manifest itself as a simple local irritation with erythema and inflammation but can also progress to erosions and ulcerations of the entire oral mucosa and are also responsible for an increased risk of infection in these immunocompromised patients. The only therapies currently offered are local care and intravenous analgesics. Studies in pediatric hematology show the effectiveness of prevention and low-dose laser treatment in chemo-induced mucositis, both in terms of reducing the number of mucositis developed but also in terms of reducing the grade of mucositis. This currently results in a recommendation for the use of photobiomodulation by international bodies such as ESMO (European Society for Medical Oncology).