Linoleic acid is a vital component in normal sebum that does what it is supposed to: Protect the skin. Skin/sebum in people (and other mammals) prone to acne and other skin problems have been found to be deficient in linoleic Acid. Sebum deficient in linoleic acid is hard and sticky and clogs pores. It looks greasy and has fewer protective and anti-inflammatory properties.

Key points: Acne and other problem prone skin (in people and animals) are lacking in linoleic acid.
Linoleic acid is a component in the ceramides that make skin strong and impermeable and thus less easily ruptured and less sensitive to irritations. This can be changed with topical application. Grape seed and Safflower oil are over 70% linoleic acid. Linoleic Acid inhibits the enzymes that convert Testosterone to DHT. Both types. So it can help with hirsutism, hairloss and acne. Linoleic Acid is anti-inflammatory and protects the skin from UV damage. Linoleic Acid inhibits melatonin and thus fades hyperpigmentation. Linoleic acid is anti-microbial as the P. Acnes blamed for acne. Linoleic acid deficiency causes an increase in interluekin -1a which is a factor inflammatory response. Tretinoin (Retin A & the like) alters the lipid profile improving the linoleic acid composition. Linoleic Acid improves the peroxisome proliferator-activated receptors (PPAR) and retinoid X receptor (RXR) situation that regulates sebum production and hyperkeritinization/differenciation (and is what accutane affects) Linoleic acid is involved in the formation of Lamellar granules that produce the enzymes involved in normal exfoliation. They also form the armor that makes your skin strong. Acne prone skin has been found to contain fewer lamellar granules. Ceramide in a deficient skin barrier is lacking a protein called sphingosine. In winter our skin produces less sphingosine which is one reason acne often worsens in winter. Topical application of live cultured yogurt can boost production. Thyroid hormone affects lipid profile. One way that perhaps both hypo and hyperthyroid conditions affect acne. We don't necessarily have a dietary or systemic deficiency in linoleic acid. Just in the sebum and thus a topical application is the best course of action. This tendency is genetic. Examples of skin problems affected by a deficiency in linoleic acid include acne, eczema, psoriasis, keratosis pilares, hypersensitivity to allergens, and dry itchy sensitive skin of all types--aka dermatitis. A What To Do About This Post

It also might repel pests like the mites responsible for many skin irritations. And hopefully mosquitos, fleas and ticks for your pets sake.

Excerpt from a good paper: ----------------- Nearly all the items in the list of roles played by linoleic acid in sebum above affect acne. i only bolded the ones that most here would recognize as causes of acne i.e. the inflammation.
Note: These oils are not stable and should be stored in the refrigerator. Get a small, preferably dark colored bottle to keep a small amount at a time in your medicine cabinet.

So, my dog is prone to itchy skin and is extremely sensitive to flea bites. Which attracts more fleas. They like dry, irritated, easily permeated skin. Most healthy animals aren't that bothered by fleas and some don't get fleas. My brother had an indoor/outdoor cat that didn't. And I have a friend with a dog and cat that don't get fleas which is amazing in this climate. So, there's probably something different about these animals. Just like there's something different about we acne prone people that makes the SAD diet leads to acne in us, but not everyone else.

I've been looking in to what I could do to improve his skin and have found information on some dogs having a deficient skin barrier because their skin is lacking a ceramide. That lead to me finding info on them lacking linoleic acid, just like acne prone skin.

And I discovered there is a topical 'spot on' treatment called Allerderm Spot on Lipid Complex For damaged epidermal barriers that involves putting a blend of lipids in a spot on the dog, usually the neck, where he won't lick it off just like with the spot on flea treatments.

That means you must be able to change your lipid profile with topically applied lipids!!!!
And you might not necessarily need to apply it directly to your acne prone skin if you don't want to. The way allerderm is not applied to the itchy skin but to some spot where the dog won't lick it off.

Since dogs can't have grapes, I'm trying safflower oil instead of my preferred grapeseed for now. The rest of you should try grapeseed. Grapeseed is a little more potentially comodogenic.

Here's some of the info and a study on dogs and Allerderm:
More info on Allerderms informaton sheet. Explains some of the ways a linoleic deficiency causes many skin conditions. (but i've found more, including acne) : http://www.virbacvet...OCT09.sflb.ashx

Dosage for Dogs and cats
6 pipettes of 2 mL each (0.068 oz) for small dogs and cats ≤ 20 lb 6 pipettes of 4 mL each (0.135 oz) for medium and large dogs ≥ 20 lb

I've been trying to find the ingredients in the spot on treatment for dogs and cats. So far, all I've found is that it contains ceramides, free fatty acids, and cholesterol without specifying which. I'm pretty sure it includes some omega 3 in addition to the linoleic acid. I've found info on capsules to be taken orally. They have a couple of formulas:

Allerderm EFA-Caps Guaranteed Analysis (per capsule): Eicosapentaenoic Acid (EPA) 80 mg, Docosahexaenoic Acid (DHA) 50 mg, Linoleic Acid (LA) 30 mg, Gamma Linolenic Acid (GLA) 18 mg, Vitamin A 800 IU, Vitamin D 25 IU, Vitamin E 11 IU
Allerderm EFA-Caps Ingredients: Fish oil, borage seed oil and sunflower seed oil (sources of fatty acids), glycerin, purified water, d-alpha tocopherol (source of vitamin E), vitamin A palmitate
Allerderm EFA-Z Plus Guaranteed Analysis (per mL): Linoleic Acid 510 mg, Vitamin A 136 IU, Vitamin E 1.9 IU, Zinc 2.1 mg, Pyridoxine HCI 0.10 mg, Biotin 2.0 µg, Inositol 0.38 mg
Allerderm EFA-Z Plus Ingredients: Sunflower seed oil, fish oil and borage seed oil (sources of fatty acids), zinc sulfate, natural and artificial flavoring, alpha tocopherol acetate (source of vitamin E), silica, propylparaben, inositol, pyridoxine HCl, vitamin A palmitate, methylparaben, biotin

A pretty good paper: Atopy, pyoderma and the skin: Barrier function and beyond....... About dogs and cats, but there's lots of reference to human skin problems and research and products for humans. There's quite a few citations at the bottom that I haven't looked at yet.