For the duration of the experiment, I consumed approximately 25mg doxycycline in the morning on top of my usual stack of supplements. Unfortunately, due to laziness and lack of time, I don’t have any objective observational data of the effects (i.e., comparative photos taken under identical conditions), so I’ll instead talk about how things appeared. I wouldn’t normally be satisfied with such subjective measurement, but the outcome was so resoundingly bad that I don’t think it matters! :/

Initially, I was perplexed that an ulcer I developed in my mouth was seeming to take far longer than normal to heal; however, this may have something to do with my expectation that healing, especially of oral wounds, would be accelerated.

The one important factor that I intended to measure was if doxycycline supplementation would do anything to increase the production of collagen in the skin. As someone who has experienced the obvious and profound (and positive) effect of oral retinoids on skin texture and quality, I was somewhat disappointed in doxycycline’s effect. Not only was there no (subjective) reduction in the number, severity, or depth of the photo-aging induced wrinkles on my face, but the doxycycline appeared to be making the condition worse!

About two weeks into the experimental period, I was continually dismayed every time I looked into the mirror at what appeared to be a ‘thinning’ of the skin on my face, particularly noticeable on my forehead, as well as more noticeable wrinkles and an overall reduction in any remnants of the youthful glow that Father Time has yet to wrestle from me. Even within the short duration of the experiment, the skin on my face started to take on that ‘papery’ stiffness one associates with the skin of the elderly.

It really was difficult to persist with the regimen in the face of what I felt to be outright failure of my idea, but I did anyway.

About ten days after ceasing the medication, I already feel my skin has mostly regained its normal texture, but I can’t be sure because I didn’t carry out any real quantitative analysis. It has definitely reverted to its normal elasticity.

All in all, I recommend not employing doxycycline to improve the quality of one’s skin. As for why this happened, I can only speculate. If we assume that doxycycline does in fact inhibit the breakdown of collagen, I suppose it could have caused a ’stiffening’ of the skin, which then caused it to appear more wrinkly and deeply lined. The perceived reduction in facial subcutaneous fat my have just been my interpretation of the changed texture. Perhaps it skews the ratio of collagen to elastin, again resulting in a reduced elasticity of the skin.

Regardless, I seem to have discovered for myself why there is apparently no research taking place regarding doxycycline as a potential ‘cosmaceutical’!

This is because, while the ability to degrade the matrix is extremely important in growth and wound healing, if the processes of synthesis and degradation fall out of balance in favour of degradation, the overall amount of collagen will decrease.

In youth, these processes are in balance, but as we age, the degradative enzyme activity begins to overpower that of synthesis, leading to a loss of skin quality. Other factors that increase MMPs are photodamage and smoking.

In the past, I’ve boosted my skin’s balance in favour of collagen synthesis with isotretinoin, which worked beautifully but has drawbacks that in my opinion make it unacceptable for chronic use (cracking lips, sun sensitivity, etc.). I’ve also heard that the skin’s response to collagen-synthesis stimulating retinoids decreases with age.

So, in theory, one could boost its overall levels by instead interfering with the breakdown of collagen by inhibiting MMPs.

At present, the only MMP inhibitor that’s available readily and cheaply is doxycycline hyclate, an antibiotic often used to combat acne. Apparently, by taking a subantimicrobial dose (i.e., too little to kill bacteria) one can benefit from its anti-MMP activity while minimizing its side effects. Doxycycline is also used in this way in dentistry, where it is used to facilitate healing of the connective tissue in the gums.

There was also a study where doxycycline’s effect on wound healing was investigated because it was suspected it may *interfere* with normal wound healing as a side-effect, but it was instead found that the wounds actually healed either at the same rate or faster.

So, lately I’ve been noticing the accumulation with age and decades of intense sunlight a slight loss of skin elasticity (yes, wrinkles), so I decided to start taking 25mg/day doxycycline for a couple of months and see if this has any effect on the quality of my skin. I’ve taken some ‘before’ photos that highlight the problem, and I intend to compare these with pictures taken in 1 and 2 months to see if I can identify any change.

The literature is at first glance almost entirely free of this kind of experiment, with most papers focussing on doxycycline’s antibacterial and anti-inflammatory effects for the treatment of acne and rosacea. I’m sure there’s a good reason for this that I in my limited capacity don’t have time to dig up, so I’m pressing ahead regardless.

I’ll post the results, including before/after shots and analysis in about a month

Here’s some reading in the meantime:

• Inhibition of matrix metalloproteinases: a new skin care frontier
• Matrix metalloproteinases
• Doxycycline