Tranexamic acid, also known as hemostatic cyclic acid, is a class of fibrinolytic plasminogen activator inhibitor and is often used clinically as an antifibrinolytic hemostatic agent. Many reports at home and abroad show that tranexamic acid has obvious efficacy in the treatment of melasma. It has been proved that tranexamic acid and tyrosinase do not have direct effect on each other, but the former is to restrain the formation of blood enzyme kinase receptor sc-uPA when keratinocytes appear, and the important function of this receptor is to promote the formation of tyrosinase and prevent the conversion of fibrinogen into fibrinolytic enzyme, so that the liaison between keratinocytes and melanocytes is affected, thus reducing the number of melanin particles transferred to keratinocytes and finally inhibiting melanin synthesis. This reduces the number of melanin particles transferred to keratinocytes and ultimately inhibits melanin synthesis. Some researchers have found that tranexamic acid mainly has the function of inhibiting melanocytes, but has no significant effect on the number of melanocytes, inhibiting the expression of melanin and thus fading the pigmentation. Hydrafacial injection method, also known as hydraluminescence, is derived from mesotherapy, and its mechanism is to use special injection needles to adsorb the skin through a negative pressure system, while injecting the agent to be injected into the designated location. Because the pressure, injection volume, injection rate and injection depth of each skin adsorption can be set by computer parameters, the operation and application are more scientific and easy to control. So will the treatment of melasma by direct injection of tranexamic acid into the deeper layers of the skin using hydrophobic injection therapy be more effective than direct oral administration of tranexamic acid? I. Selection of experimental subjects A total of 70 cases were selected for melasma treatment in our hospital, among which all the candidates met the diagnostic criteria. Among them, 63 were female and 7 were male, aged from 20 to 50 years old; the duration of the disease ranged from 1 month to 9 years, with an average of (2.1±1.1) years. The above-mentioned candidates were randomly divided into oral group and hydrophobic injection group, with 35 cases in each group. II. Pre-operative preparation All candidates signed an informed consent form before treatment, and the subjects’ facial frontal and lateral photographs were taken using the equipment and recorded for archiving respectively. Exclusion criteria: ① pregnant and lactating women; ② those with a tendency to thrombosis; ③ those who had applied other drugs in the past 3 months; ④ those with abnormal blood count and coagulation function, those with gynecological and liver disease history; ⑤ outdoor workers, scarred body and those with poor compliance. Drugs and instruments used Hydroluminescence injector, tranexamic acid injection, tranexamic acid tablets. IV. Treatment procedure Oral group of candidates are given tranexamic acid tablets (0.24g/time), 2 times/day. In the hydrophobic injection group, 0.24g of tranexamic acid was added to 3.5mL of saline, and the injection depth was adjusted to 0.8~1.2mm according to the specific location of the lesion, and the amount of each injection was adjusted according to the extent of the lesion, and the return proportion was set at 35%. The candidates in the hydrophobic injection group should not touch water locally for 3 days before the consultation and should not take any other medicine. V. Judgment method After the start of the treatment, we will follow up once a month to observe and consult the effect and side effects of the treatment. There are 4 levels of efficacy evaluation criteria. ①basic cure: spot area fades ≥90%, color is completely removed; ②effective: spot area fades ≥60%, color lightens significantly; ③improved: spot area fades ≥30%, color is lighter than before; ④invalid: spot area fades <30%, color is almost unchanged. Cure = number of basic cure cases/total number of treatment cases; efficiency = number of (basic cure+effective) cases/total number of treatment cases×100％. Clinical efficacy: the cure rate and effective rate of the oral group were 17.1% and 54.3% respectively, while the rate of the hydrophobic injection group was 22.9% and 65.7%. Adverse reactions: One case (2.8%) in the oral group showed mild gastrointestinal reactions (nausea, diarrhea), and was advised to take it after meals, and the symptoms were relieved; another case (2.8%) showed reduced menstrual flow, and was advised to take it after the cessation of menstruation and was improved. During the consultation, no adverse reactions such as skin scarring, hyperpigmentation and menstrual changes were observed in the patients of the hydrophobic injection group. VIII. Conclusion The therapeutic effect of tranexamic acid on melasma is unmistakable, and it is most commonly administered orally for consultation and treatment. A foreign researcher gave local lesion injection of tranexamic acid (4.0 mg/mL) using microinjection method for 1 time/month for 3 times and followed up for 3 months. The results showed that the melasma area and severity score in the microinjection group improved by 35.72%, with 26.09% improvement of ≥50%, which is a significant efficacy. In this validation, 35 candidates each in the tranexamic acid hydraluminescence injection group and the oral group completed the consultation as planned. Compared to the oral method, the 1 time/month treatment by hydraluminescence injection method has helped a lot in improving the compliance of the candidates, and the direct injection of tranexamic acid into the relevant areas and layers of the skin allows for smaller doses, less adverse effects, and a rapid achievement of the treatment results. Tips: The use of tranexamic acid hydroluminescence injection can effectively reduce melasma pigmentation, with good compliance, simple treatment, precise recent efficacy and no obvious adverse reactions, suggesting that this method is an effective treatment for melasma.