Use of pufas for treating skin inflammation

1. A topical composition comprising:

at least one excipient; and

a polyunsaturated fatty acid (PUFA) derivative of formula (I):

or a salt thereof, wherein:

-Alk- is:

—CH(OR 2 )-[trans]CH═CH-[cis]CH═CH—CH 2 -[cis]CH═CH—C 3 H 6 —, —(CH 2 ) 3 —CH(OR 2 )-[trans]CH═CH-[cis]CH═CH—CH 2 -[cis]CH═CH—, —(CH 2 ) 3 -[cis]CH═CH—CH 2 -[cis]CH═CH-[trans]CH═CH—CH(OR 2 )—, or

R 1 is a hydrogen atom;

R 2 is:

a hydrogen atom,

—(C═O)—R 5 , wherein R 5 is a C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 6 -C 10 aryl, 5- to 10-membered heteroaryl, C 3 -C 7 carbocyclyl or 5- to 10-membered heterocyclyl group, or R 5 is an aliphatic group having from 3 to 29 carbon atoms, or

—(CH 2 OCH 2 ) n OH, wherein n is an integer from 1 to 200;

wherein said alkyl, alkenyl, alkynyl and aliphatic groups are the same or different and are each unsubstituted or substituted with 1, 2 or 3 unsubstituted substituents which are the same or different and are selected from halogen atoms and C 1 -C 4 alkoxy, C 2 -C 4 alkenyloxy, C 1 -C 4 haloalkyl, C 2 -C 4 haloalkenyl, C 1 -C 4 haloalkoxy, C 2 -C 4 haloalkenyloxy, hydroxyl, —SR′, and —NR′R″ groups where R′ and R″ are the same or different and represent hydrogen or unsubstituted C 1 -C 2 alkyl;

wherein said aryl, heteroaryl, carbocyclyl and heterocyclyl groups are the same or different and are each unsubstituted or substituted by 1, 2, 3 or 4 unsubstituted substituents which are the same or different and are selected from halogen atoms, and cyano, nitro, C 1 -C 4 alkyl, C 1 -C 4 alkoxy, C 2 -C 4 alkenyl, C 2 -C 4 alkenyloxy, C 1 -C 4 haloalkyl, C 2 -C 4 haloalkenyl, C 1 -C 4 haloalkoxy, C 2 -C 4 haloalkenyloxy, hydroxyl, C 1 -C 4 hydroxyalkyl, —SR′ and —NR′R″ groups wherein each R′ and R″ is the same or different and represents hydrogen or unsubstituted C 1 -C 4 alkyl;

wherein the PUFA derivative is in the form of a racemate, a stereoisomer or a mixture of stereoisomers; and

wherein the topical composition is substantially free of glucocorticoids.

2. The topical composition of claim 1 , wherein R 1 is a hydrogen atom.

3. The topical composition of claim 1 , wherein -Alk- is

—(CH 2 ) 3 -[cis]CH═CH—CH 2 -[cis]CH═CH-[trans]CH═CH—CH(OR 2 )—.

4. The topical composition of claim 1 , wherein R 2 is a hydrogen atom.

5. The topical composition of claim 1 , wherein the PUFA derivative is present as the R enantiomer.

6. The topical composition of claim 1 , wherein the PUFA derivative is present as the S enantiomer.

7. The topical composition of claim 1 , wherein:

(a) R 2 is —(C═O)—R 5 , wherein R 5 is a saturated aliphatic group having from 3 to 29 carbon atoms; or

(b) R 2 is —(CH 2 OCH 2 ) n OH.

8. The topical composition of claim 1 wherein the excipient comprises a preservative selected from methylparaben, propylparaben, benzyl alcohol, ascorbyl palmitate, and ascorbic acid.

9. The topical composition of claim 1 , wherein the excipient comprises an emollient, an emulsifier, a thickener, and/or a preservative.

10. The topical composition of claim 1 , wherein the excipient comprises a solubilizing agent and/or a humectant.

11. The topical composition of claim 1 , wherein the topical composition is in the form of a cream.

12. A method of treating skin inflammation in a mammal comprising administering to skin of said mammal the topical composition of claim 1 .

13. A topical composition comprising 15-HETrE or an ester thereof and an excipient.

14. The topical composition of claim 13 , wherein the excipient comprises an emollient, an emulsifier, a thickener, a preservative, a solubilizing agent, and/or a humectant.

15. The topical composition of claim 13 , wherein the topical composition is substantially free of glucocorticoids.

16. The topical composition of claim 13 , wherein the topical composition is in the form of a cream.