Wash your clothing and then wash your hands after handling the dirty clothes.A second line of defense is to avoid sunlight, so as not to activate a phototoxic substance:

If you come in contact with a phototoxic substance, immediately wash the affected area with soap and cold water, and avoid any further exposure to sunlight for at least 48 hours. Heat and moisture can worsen the skin reaction, which is why it’s important to wash the affected area with soap and cold water. Stay indoors, if possible. Be sure to avoid light shining through windows. If staying indoors is not an option, cover the affected area with sun protective clothing. In lieu of sun-protective clothing, apply sunscreen to the affected areas after washing.Phytophotodermatitis is triggered by long wavelength ultraviolet light (called UVA) in the range of 320–380 nanometers, so the best sun-protective clothing and sunscreen products will block these wavelengths of UVA radiation. In 2011, the U.S. Food and Drug Administration (FDA) established a "broad spectrum" test for determining a sunscreen products UVA protection. Sunscreen products that pass the test are allowed to be labeled as "Broad Spectrum" sunscreens, which protect against both UVA and UVB rays. There is no equivalent test or FDA-approved labeling for sun-protective clothing. Some clothing is labeled with an Ultraviolet Protection Factor (UPF) but test results from Consumer Reports suggest that UPF is an unreliable indicator of UV protection. Treatment
Many different topical and oral medications may be used to treat the inflammatory reaction of phytophotodermatitis.
Phytophotodermatitis, also known as berloque dermatitis or margarita photodermatitis, is a cutaneous phototoxic inflammatory reaction resulting from contact with a light-sensitizing botanical agent followed by exposure to ultraviolet light (from the sun, for instance). Symptoms include erythema, edema, blisters (vesicles and/or bullae), and delayed hyperpigmentation. Heat and moisture tend to exacerbate the reaction. A reaction may be elicited in any person who has been exposed to adequate amounts of both a photosensitizer and ultraviolet light. Phytophotodermatitis is not an immunologic response; no prior exposure to the photosensitizing agent is required. The photosensitizing substances found in phototoxic plants belong to a class of chemical compounds called the furanocoumarins, which are activated by long-wavelength ultraviolet (UVA) light. The most toxic of these organic compounds are the linear furanocoumarins, so called since they exhibit a linear chemical structure. Bergapten and xanthotoxin (also known as methoxsalen), two linear furanocoumarins derived from psoralen, are invariably found in plants associated with phytophotodermatitis. Symptoms and signs
A reaction typically begins within 24 hours of exposure and peaks at 48–72 hours after exposure. Initially, the skin turns red and starts to itch and burn. Large blisters (or bullae) form within 48 hours. The blisters may leave black, brown, or purplish scars that can last for several years. This hyperpigmentation of the skin is caused by the production of melanin triggered by the furanocoumarins.