Does 5% liquid minoxidil work better than the foam? Most research I've read says both show similar results?

There might be a slightly increased absorption in the liquid versus the foam. The foam does not contain propylene glycol which helps in absorption. The advantage of the foam is it is less irritating and the minoxidil can be used twice a day which produces better results than a once a day application.PRP hair md.com

The long term effect is the same with both, I do find that some people have less irritation with the foam but no scientific evidence of why that is, the additive ingredient may vary causing application use (such as alcohol)  to be different but the medicine (minoxidil 5%) is the same,

Thank you for your question. You’re asking about the relative benefit of 5% minoxidil liquid compared to 5% foam. You've done research which shows comparable results, and yet you still have questions about the effectiveness based on the deliverability of the product to the scalp, and the ingredients affecting this bioavailability.
This is a kind of question that certainly comes up in my practice. A little background: I’m a Board-certified cosmetic surgeon and Fellowship-trained oculofacial plastic and reconstructive surgeon. I have been in practice in Manhattan and Long Island for over 20 years. I am also the founder of TrichoStem™ Hair Regeneration Centers based on a system of helping hair loss in both men and women with mostly androgenetic, or genetic pattern hair loss using a stem cell technology of platelet-rich plasma (PRP) and Acellular matrix. This treatment was originally derived from helping hair transplant patients expedite the healing from transplant surgery. We treat patients from all over the world, and the management of hair loss is really the core of what we’re doing over the past 8 years since the  development of this treatment, so questions about minoxidil, and finasteride for men are things we deal with every day.
The details of a question like this when you look at dermatology-based studies comparing one versus another, like liquid versus foam, or combinations where other ingredients such as retinols and topical progesterones have been added, it’s challenging to get a clear, absolute answer. Generally, these studies are relatively small in number, so statistical differences are hard to achieve. There is also a limit of what topical minoxidil can do.
Topical minoxidil, as you likely know, was derived from the use of minoxidil as an antihypertensive medication, where like our Hair Regeneration treatment, there was a pleasant side-effect of a hair growth. To this day, the mechanism in which minoxidil works remains unclear. There is a pharmacologically induced improvement of scalp coverage typically in the crown area and beyond when topical minoxidil is applied regularly.
Generally, the reason the foam was developed had to do with scalp irritation from active ingredients necessary to breakdown the top layers of the skin called propylene glycol. This chemical in the liquid form can be irritating for some people, which all doctors managing hair loss are familiar with. Patients will sometimes complain of redness, have folliculitis, or have other problems, so the use of a foam came in very handy. From my perspective, I think there pretty much comparable results from both liquid and foam. I generally tell my patients who are committed to using the foam to continue using the foam.
It’s important to have a global understanding of your hair loss progression. Over the course of 8 years or so we’ve done Hair Regeneration from a system we developed when we were using Acellular matrix and platelet-rich plasma (PRP) derived from your own blood. We initially wanted the outcome of hair transplant patients to improve with having hair grafts and donor area to heal better, and expedite the healing process. We also found out that thinning hair became thicker.
It took a lot more work to figure out how this treatment can be dosed and adjusted to make it consistent for men and women of all ages, and all ranges of degrees of hair loss. Over this time, I developed a classification system that factors in current age, age of onset of hair loss, degree of progression, rate of progression, and other medical problems we apply when we manage our patients.
One thing to be really mindful of is hair loss is progressive. If you are fortunate enough to have slow progression, then you have a certain amount of breathing room in terms of scalp coverage using minoxidil as a standalone treatment. Generally, when patients come to us for an evaluation, and have already tried a lot of treatments including minoxidil, they’re often aware for the first time the relative extent of their hair loss which often comes as a shock. It’s important to be as proactive as possible when it comes to managing hair loss.
I always explain to everyone that there is no cure for hair loss, but there is a strategy for optimal management. Whether you’re using a pharmaceutical, if you’re male using finasteride and minoxidil, or using a stem cell-based technology like Hair Regeneration, or doing surgical transplantation, you are trying to achieve maximal coverage. It is also critical to maximize the longevity of your existing hairs with whatever tools that are available, so this is where it becomes a clinical discussion with the patient of what they’re comfortable with, and how motivated they are.
Understand that you can take some comfort in knowing that minoxidil foam is an effective treatment in the management of your hair loss, but also learn about the use of a DHT-blocker like finasteride, and the technology of Hair Regeneration we have become very well known for. Patients come to us from all over the world, and we developed a system to maximize the longevity and coverage of their progression of hair loss.
Often people do things to treat their hair loss, and miss a very important window of opportunity when they could've done something. Now that these treatments are well established, it is often their hindsight that patients realize they could've done intervention sooner. A lot of our patients when they come to us, where we take a lot of pictures like from the top of the scalp, very often they have a lot more hair loss than they thought they had. When it comes to both male and female pattern hair loss, it affects the whole scalp, but the progression is variable in the expression. You may see receding temples, and think you have a small bald spot. Iif your hair is wet, you may realize the scalp has a lot less hair than it did 5-10 years earlier. Therein lies a window where you could explore these other treatments.
Learn more about the other options, and you can probably take some comfort in trying the minoxidil foam. If you still feel the liquid is the way to go, then certainly go ahead with the liquid. Understand that the thinking behind that is to try to avoid skin irritation, and hopefully you’ll be able to hold onto your hair longer than your genetic plan. I hope that was helpful, I wish you the best of luck, and thank you for your question.

These two formulations work pretty similarly. Studies have shown that more women prefer the foam over the liquid as it tends to be a bit more comsetically acceptable.

I find that for most people who use the foam, they don't get it as much on the scalp as they do when they use the liquid and separate the hair during the application