Sudden White Spots on Your Skin? 7 Common Causes

First of all, let’s not scare ourselves! The appearance of white patches on the skin, in dermatological terms, is called hypopigmentation or depigmentation, and there are actually many causes.

Today, let’s talk in detail about the most common situations, so that everyone has a bottom in their hearts and knows whether to see a doctor or not.

Post-inflammatory hypopigmentation

This refers to the phenomenon of hypopigmentation or depigmentation of the skin due to various reasons.

Common causes include:

That is to say, such “white patches” often appear in areas of the skin that have had “issues” before.

It is usually manifested as hypopigmented macules or patches, matching the shape and distribution of the previous inflammatory skin lesions.

Post-inflammatory hypopigmentation is usually reversible, and it recovers spontaneously within weeks to months after the underlying disease subsides.

⚠️ However, pigmentary demarcation caused by complete loss of melanocytes will not improve gradually. If appearance improvement is desired, epidermal grafting treatment can be chosen.

Pityriasis alba

This is a common benign skin disease, mainly seen in children and adolescents, and is more noticeable in people with darker skin tones. Pityriasis alba is often considered a mild manifestation of atopic dermatitis, but it can also be seen in non-atopic individuals.

Face, neck, arms and other areas are prone to some circular or oval light white patches, which may have had mild erythema and desquamation before.

Pityriasis alba is a self-limiting disease, which means it can heal itself, but the time required for resolution ranges from several months to several years.

Tinea versicolor

It is also known as pityriasis versicolor, commonly referred to as Tinea versicolor. This is a common, recurrent dermatophyte infection, most commonly seen in adolescents and young adults, caused by the skin’s normal flora, Malassezia yeast.

Tinea versicolor can manifest as light white, brown, or red macules and patches, mainly involving the upper trunk.

* Malassezia has lipophilic properties, and the sebaceous glands in the upper body skin secrete more vigorously, which may explain why the disease is more prevalent in the upper body. This also explains why children and the elderly, who have less sebum secretion, are less likely to develop tinea versicolor.

The mechanism leading to hypopigmentation may be related to a dicarboxylic acid produced by Malassezia – azelaic acid, which may inhibit or destroy melanocytes to some extent, contributing to hypopigmentation. Pigmented and erythematous lesions may be due to the host’s inflammatory response to the yeast.

Dermatologists can make a preliminary diagnosis based on skin rash characteristics, and
fungal microscopy can confirm the diagnosis. About 1/3 of the cases show yellow to yellow-green fluorescence under Wood’s lamp examination.

Treatment:

Vitiligo

Vitiligo is a relatively common acquired pigmentary skin disease. There are several theories explaining the destruction of melanocytes in patients with vitiligo, including genetic, autoimmune, neural, biochemical, oxidative stress, viral infections, and melanocyte detachment mechanisms.

At present, the disappearance of melanocytes in the skin lesions of vitiligo patients may be caused by multiple mechanisms, and vitiligo may actually represent a spectrum of diseases, and the familial aggregation of vitiligo suggests a genetic basis for the disease.

In addition, repeated mechanical trauma(rubbing) and other types of physical trauma(e.g., scratching, long-term pressure, or cuts) can induce vitiligo on the neck, elbows, ankles, and other parts. This is called the Koebner phenomenon, also known as the “isomorphic response“. It is reported that 20%-60% of vitiligo patients have the Koebner phenomenon.

Vitiligo usually manifests as milky white or chalk white asymptomatic depigmented macules and patches, lacking clinical signs of inflammation. Vitiligo shows a clear, bright blue-white fluorescence underWood’s lamp.

Patients may have severe sunburn, pregnancy, skin trauma and/or emotional stress before the onset of the disease. Lesions can occur at any age and any part of the body, but are more common on the face and around orifices(e.g., around the mouth, eyes, and anus), genitals, and hands. The size of the lesions ranges from a few millimeters to several centimeters, with raised edges and clear boundaries with the surrounding normal skin.

The treatment of vitiligo requires a detailed assessment and joint decision-making between the doctor and the patient.

In simple terms:

✅ For patients with rapidly progressive vitiligo with depigmented macules spreading in weeks or months, systemic use of glucocorticoids(e.g., dexamethasone, prednisone, etc.), immunosuppressants(e.g., cyclosporine, mycophenolate mofetil, etc.) is used to stabilize rapidly progressive vitiligo. In addition, biologics such as oral JAK inhibitors are also tried clinically to stabilize vitiligo, but oral JAK inhibitors have not yet been approved for the indication of vitiligo.

✅ Topical use of corticosteroids(e.g., mometasone furoate), calcineurin inhibitors(e.g., tacrolimus), JAK inhibitors(ruxolitinib), and ultraviolet phototherapy are commonly used measures to stabilize, alleviate vitiligo, and repigmentation.

Nevus depigmentosus

Nevus depigmentosus, also known as achromic nevus, is a benign skin lesion that is often discovered shortly after birth or during infancy, caused by a lack of skin pigment cells.

It usually manifests as irregularly shaped hypopigmented macules. UnderWood’s lamp, it appears as bright white or light fluorescence, contrasting sharply with the surrounding skin. Unlike nevus anemicus, the difference between the lesion and the adjacent normal skin remains after glass slide pressure.

Generally no treatment is needed, and there is currently no effective drug treatment. For aesthetic reasons, camouflage agents can be used for cosmetic coverage.

Halo nevus

Halo nevus (Sutton’s nevus), also known as acquired centrifugal hypopigmentation, is a type of melanocytic nevus surrounded by a circular or oval, usually symmetrical white halo (depigmented halo).

This white halo often implies that the body’s immune system may have begun to “attack” the nevus, indicating that the nevus may gradually regress.

The halo nevus is characterized by a central nevus, which may be flat or raised, with a diameter of a few millimeters to several centimeters, surrounded by a depigmented halo.

The depigmented halo is usually symmetrical and may gradually expand over time, with the central nevus becoming lighter or even disappearing.

The halo may be a few millimeters to several centimeters wide, and the edge is often irregular and not sharply demarcated from the surrounding skin.

Under Wood’s lamp, the depigmented halo appears as a bright white or light fluorescence, contrasting sharply with the surrounding skin.

Halo nevi are generally benign and do not require treatment unless there is a cosmetic concern or suspicion of malignancy.

If there is a suspicion of malignancy, a skin biopsy should be performed to confirm the diagnosis.

For cosmetic reasons, if the nevus is small, it can be completely excised and sutured.

If the nevus is large, other treatments such as cryotherapy, laser therapy, or imiquimod cream may be considered.

Idiopathic guttate hypomelanosis

Idiopathic guttate hypomelanosis is a common benign skin condition characterized by multiple small, discrete, asymptomatic hypopigmented macules on the sun-exposed areas of the body, particularly on the extremities.

It is more common in older adults and is considered a type of post-inflammatory hypopigmentation.

The exact cause is unknown, but it may be related to chronic sun exposure, genetic factors, and other unknown factors.

The lesions are typically 1-5 mm in diameter, round or oval, and may be slightly depressed below the surface of the skin.

They are most commonly found on the extremities, particularly on the shins and forearms, but can also occur on the trunk and face.

The color of the macules ranges from white to hypopigmented, and they are usually asymptomatic.

No specific treatment is required for idiopathic guttate hypomelanosis, as it is a benign condition and does not pose a health risk.

However, if there is a cosmetic concern, treatments such as cryotherapy, laser therapy, or topical corticosteroids may be considered.

Sun protection is also important to prevent the development of new lesions.