The skin eruption appears acutely with redness, swelling and clutches of small vesicles (very small blisters). In severe cases there may be extensive blistering, scaling, and weeping. In chronic milder disease, papules (raised spots) and scaling are more prominent. The lesion is itchy and may be painful if severe. The rapidity of onset after contact is directly proportionate to the degree of sensitivity and may range from six hours to several days.

The location of the eruption on the skin is helpful in diagnosing the cause. Certain areas of skin, such as the eyelids, react more easily than others, such as the palms. Metal dermatitis, usually caused by sensitivity to nickel, appears in discrete patches corresponding to the area of contact with jewelry, watches, or metal objects on clothing. A variety of allergens , such as dyes and fabric finishes, are found in clothing, causing a skin eruption on areas of skin covered by the apparel. Volatile allergens, such as perfumes and essential oils, affect exposed areas, usually the face and arms. Rhus dermatitis from poison oak or poison ivy, native to North America, produces an especially severe disease with prominent vesicles and large blisters. Characteristic streaks of vesicles arise that correspond to brushing of the skin by the plant leaves.

The main symptoms of contact dermatitis are the appearance of a rash accompanied by an itchy, burning sensation and swelling. The rash may develop into clusters of red papules (raised spots) or, in severe cases, blisters. Scratching of the rash causes exudation (leakage) and an exacerbation of the irritation. On rare occasions, swelling and tenderness of the eyelids, lips and perineum can occur.

Contact dermatitis usually results in excessive stimulation of body functions. It is described in TCM as an asthenia syndrome and results from a relatively strong body-resistance in fighting excessive pathogens . The usual presentation in an asthenia syndrome is fever, thirst, irritability, abdominal discomfort, constipation and dark-colored urine. Severity varies with the progression of the disease.

TCM practitioners will examine the sufferer and categorize the symptoms under special syndrome groups known as "disharmony patterns." Certain disharmony patterns are present during the different stages of the disease. Contact dermatitis can be classified into the following types:

Excessive fire accumulation
This form of contact dermatitis presents with acute onset. The skin at first appears pink, or with a red rash, and there is a distinct margin and edematous accumulation of fluid in the tissues base. The rash then develops into clusters of papules (raised spots) and is accompanied by a burning sensation and itchiness. Associated systemic symptoms include mouth dryness, thirst, fever, irritability, dark urine and constipation.

Excessive fire mixed with dampness
This is a more serious form of the condition. The red papules are edematous and blisters develop which may be as large as an egg-yolk. If the rash is scratched, fluid will leak out. The rash can be extremely itchy and the lesion may become swollen and create a sensation of burning. Systemic upset includes mouth dryness and poor appetite.

Blood deficiency accompanied by wind and dryness accumulation
With repeated relapses of the disorder, the skin lesions become thickened, dry and scaly. The lesion may also develop lichen-like changes (skin develops a thickened leathery appearance). The severity of the irritation results in scars on the skin from excessive scratching.