Topical drug therapy is one of the most commonly used therapies in the treatment of dermatological diseases, and glucocorticoids are often used externally to treat dermatitis eczema-like diseases or other skin diseases because of their anti-inflammatory and anti-itching effects. However, topical glucocorticosteroids are absorbed transdermally and may produce a series of external or internal adverse effects such as skin atrophy, capillary dilation, hypertension and osteoporosis, so it is especially important to control the dosage of topical glucocorticosteroids. In the past, dermatological treatment lacked uniform standards, and doctors often told patients how to control the dose through experience, which lacked scientificity and operability. If the doctor did not give a full course of topical glucocorticoid preparation regimen, then the patient may feel that the disease cannot be cured or think that the doctor’s therapy is not good because the expected efficacy is not achieved after using the medicine; if the dosage given by the doctor greatly exceeds the dosage required for the expected efficacy, then it will cause a waste of medicine and may even lead to medical disputes due to the refund of the remaining medicine. In this context, in 1991 Long et al. introduced the concept of “Fingertip Units” (FTU), which provides a feasible guideline for dermatologists to inform patients about the correct dosage of topical glucocorticoid preparations. “Long [4] et al. defined an FTU as the amount of ointment that can be extruded from a standard topical ointment tube with a 5-mm diameter orifice to cover the distal phalangeal fold of the index finger to the tip of the index finger. 1 FTU weighs approximately 0.5 g. Subsequently, the authors, for the sake of operational convenience, introduced the hand area commonly used in burn units in the past. The concept of hand area was introduced and used in correspondence with the FTU, i.e., the area of the hand was used to estimate the area of the lesion in dermatological patients and thus the amount of ointment required. The one-sided area of the hand is defined as 1 hand area, which is approximately 1% of the body surface area, i.e., 1 hand area = 1% of the body surface area. Therefore, 2% of the body surface area (2 hand areas) requires 1 fingertip unit to cover, followed by 1 hand area of skin surface requiring 0.5 FTU or 0.25 g of ointment, while 4 hand areas equal 2 FTU or 1 g of ointment, i.e., 4 hand areas = 2 FTU = 1g . The human body has different FTU values for different age groups and different areas. 1 FTU for an adult male = 0.5g, 1 FTU for an adult female = 0.4g, while 1 FTU for a 4-year-old child is about 1/3 the amount of 1 FTU for an adult male, and 1 FTU for a 6-month to 1-year-old infant is about 1/4 the amount of 1 FTU for an adult male. Using the end of the index finger of adult males as the standard, a single hand = 1 FTU, a single upper limb = 3 FTU, a single foot = 2 FTU, a single leg = 6 FTU, the face and neck = 2.5 FTU, the front and back of the trunk (including the buttocks) = 14 FTU, and the whole body = 40 FTU. Schlagel et al. concluded that 1 g of cream can cover 100 cm2 of skin, and an average height adult whole body skin surface can be covered by about 20 to 30 g of ointment. So how to calculate the dose of glucocorticoid topical hormone use in practice? Let us illustrate with an example. For example, to treat a patient with a lesion area of 8 adult hands, the dose of ointment should be 4 FTU per application, i.e. 2 g. If applied once daily, a 30 g ointment can last for about 15 days, while if applied twice daily, the same ointment can only last for a week. If an adult female uses the cream once a day and applies it to both upper extremities, the dosage is 2.4 g per day (2 upper extremities x 3 FTU x 0.4 g) and 16.8 g per week (7 x 2.4 g), a 30 g cream will last for two weeks; however, if she uses it twice a day (4.8 g/d), the cream is less than a week (33.6 g/w). If an adult male uses the cream once a day on both hands and feet, he would use about (2 feet x 2 FTU + 2 hands x 1 FTU) x 0.5 g = 3.0 g per day, which is 21 g per week. Although FTU is a concept proposed for glucocorticoid topical preparations, it is also a guide for dermatologists in applying non-glucocorticoid topical preparations. For example, carbotriol cream (15g/pc), which is used for the treatment of psoriasis, has dosage restrictions, and the instructions state that the weekly dosage should not exceed 100g, i.e. the average daily dosage should not exceed 14g.