Brown spots on the palms, medically termed palmar hyperpigmentation, are a frequent concern. The skin on the palms (acral skin) is distinct because it is thicker and lacks oil glands, which affects how discoloration manifests. Hyperpigmentation results from an accumulation of the pigment melanin in the skin layers. While many causes are harmless and localized, the unique nature of this area means certain spots require careful attention, as they can sometimes signal a more serious underlying issue.
Benign and Localized Skin Reactions
The most frequent reasons for brown spots on the palms relate to external factors or local skin trauma. Post-inflammatory hyperpigmentation (PIH) is common, resulting from excess melanin production in response to prior injury, irritation, or inflammation. This localized darkening can follow a burn, eczema, or repeated friction. The discoloration typically corresponds directly to the damaged area.
Lentigines, often called “age spots,” are flat, brown macules caused by increased melanocytes. Though more common on the back of the hands, they can appear on the palms. Tinea nigra is a less common, benign cause, presenting as a painless, non-scaly dark brown or black patch, often found on only one palm.
Physiological pigmentation, or normal variations in skin tone, can contribute to palmar darkening, especially in individuals with darker skin types. Phytophotodermatitis causes hyperpigmentation after skin exposure to certain plant compounds (like those in limes or celery) followed by sunlight. This localized reaction leaves behind temporary dark patches.
Systemic Conditions and Medication Effects
Brown spots on the palms can be a visible manifestation of an internal health issue or a side effect of pharmaceutical treatment. These spots are often symmetrical or widespread, indicating a systemic process. Addison’s disease, involving adrenal insufficiency, is a known endocrine cause. Decreased cortisol leads to increased melanocyte-stimulating hormone, causing generalized skin darkening often pronounced in skin folds and the creases of the palms.
Certain medications induce hyperpigmentation by increasing melanin production or depositing the drug or its metabolites in the skin tissue. Chemotherapeutic agents, such as fluorouracil and capecitabine, are known to cause diffuse hyperpigmentation on the palms and soles. Other implicated drugs include specific antimalarials, tetracycline antibiotics like minocycline, and certain anti-arrhythmic medications.
Systemic iron overload conditions like hemochromatosis can lead to a bronze or grayish skin discoloration that may affect the palms. Nutritional deficiencies, particularly a lack of vitamin B12, have also been associated with hyperpigmentation of the palms.
High-Risk Spots and Malignancy
Any new, changing, or unusual pigmentation on the palm warrants prompt professional evaluation due to the risk of malignancy. Acral Lentiginous Melanoma (ALM) is a serious, uncommon form of skin cancer that develops specifically on the palms, soles, or under the nails. It is the most common subtype of melanoma found in individuals with darker skin tones.
ALM often presents as a flat, irregularly shaped patch of brown, black, or mixed color. Key warning signs are based on the “ABCDE” criteria, adapted for acral surfaces:
- Asymmetry (the spot cannot be folded into two matching halves).
- Border irregularity (the edges are notched or scalloped).
- Color variability (multiple shades of brown, black, or red/blue within the lesion).
- Diameter (lesions larger than 6mm are of concern).
- Evolving or Elevated characteristics (any change in size, shape, color, or texture).
Diagnosis and Management
Diagnosis begins with a detailed medical history and visual examination by a dermatologist. A dermoscope is used to examine the lesion with magnification and specialized lighting, helping distinguish benign patterns from those suggestive of malignancy. If the spot exhibits concerning features or the diagnosis is uncertain, a skin biopsy is performed for definitive microscopic analysis.
Management depends entirely upon the underlying cause. For benign causes like post-inflammatory hyperpigmentation, treatment involves topical agents such as hydroquinone or retinoids, alongside addressing the initial source of trauma. If a systemic disease, such as Addison’s disease, is the root cause, hyperpigmentation is managed indirectly by treating the internal condition. If medication is the cause, pigmentation may resolve after the drug is discontinued. Confirmed Acral Lentiginous Melanoma requires surgical excision with clear margins.