Why Do Humans Have Weak Sense of Smell

Compared to nearly all other animals, humans have the weakest sense of smell. You would think that humans and our closest evolutionary cousins (chimpanzees, apes, etc) would have similar sense of smell, but humans still have a much weaker olfactory sense.

Why might that be?

Well, research from Karolinska Institutet have discovered that humans are the ONLY mammals whereby no new neurons are formed in the olfactory bulb after birth. Or if there is any, it is VERY little.

In all other mammals including apes, new neurons are constantly being formed in the olfactory bulb which might explain why all mammals with the exception of humans have a superb sense of smell.

How did scientists figure out the absence of neuron growth in humans?

They looked at Carbon-14 levels within the DNA of the olfactory bulb. Carbon-14 levels in the atmosphere increased significantly due to nuclear bomb testing during the Cold War.

As such, IF new neurons were being formed, one would expect Carbon-14 levels which gets incorporated into developing DNA, to be similar to current atmospheric levels. Or at least find a certain turn-over percentage of both "old" and "new" neurons reflective of the Carbon-14 atmospheric levels at time of neuron development.

However, what researchers have found was Carbon 14 concentrations that corresponded to the atmospheric levels at the time of birth of the individuals establishing that there is very limited, if any, postnatal neuron development in the human olfactory bulb.

Reference:
The age of olfactory bulb neurons in humans. Neuron. May 24, 2012, 10.1016/j.neuron.2012.03.030

Steroid and Anti-Histamine All-In-One Nasal Spray!

Meda Pharmaceuticals has announced a new nasal spray "Dymista" that contains both a steroid and an anti-histamine active ingredient. Why is this significant? It's because it's the first and only one to do so. Of course, it's not available yet until the FDA approves it, but at least it has shown effectiveness in Phase 3 clinical trials.

At this time, nasal sprays as it relates to nasal allergies come in two separate flavors:

1) Steroid Nasal Spray (flonase, nasonex, nasacort, rhinocort, veramyst, omnaris, etc, etc)
2) Anti-Histamine Nasal Spray (patanase, astepro, astelin)

This new combo nasal spray "Dymista" contains fluticasone and azelastine. Fluticasone is a steroid that is also found in flonase nasal spray whereas azelastine is an anti-histamine also found in astepro and astelin nasal sprays.

Clinical trials in the past have shown that using a steroid nasal spray and an anti-histamine nasal spray was more effective than using one or the other individually.

Similarly, Dymista has also been found to be better than either nasal spray alone, but with the convenience of using a single nasal spray.

Look for it in the near future! Let's just hope insurance will cover it however.

Read the press release here.

Reference:
Onset of Action of MP29-02 in the Treatment of Seasonal Allergic Rhinitis. J Allergy Clin Immunol 2011; 127; 2; Abstracts 199

MP29-02 in the Treatment of Nasal Symptoms of Seasonal Allergic Rhinitis. J Allergy Clin Immunol 2011; 127; 2; Abstracts 199

Combination therapy with azelastine hydrochloride nasal spray and fluticasone propionate nasal spray in the treatment of patients with seasonal allergic rhinitis. Annals of Allergy, Asthma and Immunology, 2008, vol. 100, no. 1, pp. 74 - 81.

A New Method of Allergy Testing (Multi-Array Chip Technology)

A MIT researcher has developed a new and possibly more accurate blood test for allergies using multi-array chip technology. The paper is titled "Multidimensional analysis of the frequencies and rates of cytokine secretion from single cells by quantitative microengraving" and is published in the journal Lab on a Chip.

This chip technology uses a microscopic engraving process to create thousands to millions of tiny wells (or multi-array) on a chip where a different "blood test" can occur in each well. An overly simplified explanation of how testing occurs is as follows:

Inside each well, the chip manufacturer can place a different type of food or pollen protein such as milk or cat dander. A blood sample placed into the well will than allow allergic cells to "react" with the protein. If the cell (and therefore the person) is sensitized to the protein, the cell will release chemicals called cytokines that can be measured.

Given there are thousands to millions of wells, all of them microscopic in size, only a small amount of blood can be used to test for a whole array of food and pollen allergies.

Read the actual research here.

Unfortunately, our office does not utilize this innovative technology... yet... to test people for allergies. We use RAST. Using the results obtained, we are able to provide allergy shots or allergy drops.