text: the tanning lotion of the present invention may be colorless or it may be pigmented with a desired color . upon exposure to sunlight or other source of ultraviolet radiation , the photochromic compounds undergo a photochemical change from clear or colorless to colored , thereby producing the appearance of a tan . at the same time , the molecules in the photochromic compounds open up to form a “ shield ” and protect the skin from the harmful effects of uv . in addition , sunscreen actives can be included in the formulation , if desired , although care will need to be exercised to insure that the sunscreen actives do not entirely block the uv radiation from the photochromic compounds , thereby preventing them from changing color . some blockage or screening may be acceptable to achieve a more gradual color change , for example . thus , the lotion of the invention enables a person to have the appearance of a tan , while at the same time protecting him or her from the harmful effects of exposure to uv . upon return indoors , or away from exposure to uv , the “ tan ” gradually fades as the photochromic compounds undergo a photochemical change to their colorless state . the time required for this fading to occur can be manipulated by appropriate design of the formulation , whereby after removal from exposure to uv , the “ tan ” can last for several minutes or several days , as desired . similarly , the formulation can be designed so that the photochromic compounds react immediately upon exposure to uv , or so that they react only after elapse of a predetermined time , or so that a series of sequential reaction times are obtained so that the appearance of color is gradual and mimics the natural tanning process . by appropriate selection of the spf in the lotion , some exposure to uv may be permitted so that the skin gradually tans . after a desired tan has been obtained , a lotion containing maximum spf may be applied to eliminate further exposure to uv . to produce the lotion of the invention , a photochromic compound is mixed with any skin cream , sunscreen , moisturizing lotion , or other composition , e . g ., water and mineral oil , to produce a cream , lotion or spray lotion , as desired , having suitable photostability and photoprotection . the photochromic compound is preferably selected from the spiropyrans and spiroxazine groups of the photochromic family of compounds , such as those disclosed in u . s . pat . no . 5 , 581 , 090 , for example . the spiropyrans and spiroxazine compounds normally appear as colorless but undergo photochemical transformation and exhibit intense colors when exposed to uv radiation . by appropriate selection of these compounds , various “ tan ” colorations can be obtained . the spiropyrans or spiroxazine compounds may be added to the formulation in a proportion of about 0 . 1 to about 1 . 0 percent by weight . higher concentrations yield more intense colors . different color hues are obtained by mixing two or more spiropyrans or spiroxazine compounds in the carrier , as necessary or desired . the photochromic compounds may be microencapsulated in accordance with conventional techniques so that they are not subject to the action of uv until they have been exposed by the action of rubbing the lotion onto the skin , whereby they may undergo photochemical transformation only after being applied for use . a commercially available stabilizer , such as tinuvin 765 or tinuvin 144 hindred amine by cibra - geigy corporation of new york , light stabilizers of polymers , may be added to the composition to reduce oxidation processes and thereby extend the useful life of the photochromic compound . tinuvin 765 and tinuvin 144 hindred amine light stabilizers , available from the additive division of ciba geigy . the stabilizers may be added in a proportion of from about 2 . 5 % up to about 3 . 0 % by weight . conventional sunscreen formulations which may be used in the invention include a uv absorber or blocker , and may include a pigment and an emollient . in order to get the most protection out of sunscreen combinations , the formulator can use suspoemulsions to combine amphiphilic microfine titanium dioxide with organic sunscreens using relatively small amounts of sunscreen actives . one or more sunscreen actives may be selected from the following : aminobenzenic acid , avobenzone , cinoxate , dioxybenzone , homosalate , menthyl anthronilate , octocrylene , octyl methoxycinnamate , octyl salicylate , oxybenzone , padimate , phenylbenzinadazole sulfonic acid , sulisbenzone , trolamine salicylate and zinc oxide . emolients with medium polarity are preferred so that a desired viscosity can be maintained in a narrow range over a wide concentration range of titanium dioxide . the formulation can be thickened by using polyquat 37 and propylene glycol . the use of photochromic compounds in a tanning lotion has a synergistic effect , i . e ., it is believed that when the photochromic compound molecules open up on exposure to uv rays , they will have a blocking effect on the uv rays in addition to changing color . while particular embodiments of the invention have been illustrated and described in detail herein , it should be understood that various changes and modifications may be made to the invention without departing from the spirit and intent of the invention as defined by the scope of the appended claims .