Hay fever index

Spring is coming to an end and summer is quickly approaching. Nature is blooming and there are plenty of grass pollen, too. People who suffer from hay fever sneeze, have blocked noses and itchy eyes as an allergic reaction to the pollen from trees and grasses which are released into the air. As more and more people are suffering from allergies including hay fever, this is becoming a growing problem in society. More insight is needed.

Existing sources such as the Hay Fever Radar and surveillance data from Dutch health care research institute NIVEL do provide insight into pollen flows and number of hay fever patients who visit a GP.
Not everyone who has hay fever related complaints will visit a GP and a pharmacy. They may also go to the local drugstore for self-medication products. This could be medication in the form of tablets, nose sprays or eye drops which curb the allergic reaction.
For this publication, the CBS Centre for Big Data Statistics (CBDS) studied whether weekly sales data on hay fever medication at pharmacies could be used as a new source in order to provide an overview of how the hay fever season progresses.

Increased sales

In the figure below, the turnover index for hay fever medication shows the development of weekly sales of hay fever medication relative to the average weekly turnover in 2016. The same figure displays the changing count of allergenic pollen in the air (source: Pollen counts at Elkerliek Hospital) It also shows the pollen counts of tree and plant varieties which trigger moderate, severe or very severe allergic reactions, such as the hazelnut tree, alder, birch, Poaceae, Rumex, Plantago, Cedar of Lebanon, Artemisia and Ambrosia.

 Turnover index medication (2016=100)Most allergenic pollen per m3 of air
2016 126.524
2016 223.43
2016 322.413
2016 424.3107
2016 527.51013
2016 632.9269
2016 730263
2016 835.2179
2016 934.9133
2016 1065.9276
2016 1195.3303
2016 1273.4199
2016 1392.442
2016 14134.71177
2016 15228.43475
2016 16179.9363
2016 17108.6282
2016 18326.3711
2016 19373.3231
2016 20182.9204
2016 21259.785
2016 22510.4506
2016 23561.1563
2016 24159.939
2016 25142.1167
2016 261130
2016 27135.2510
2016 28119.1195
2016 29123181
2016 3088.416
2016 3168.768
2016 3262.198
2016 3367.782
2016 3465.1105
2016 3557.273
2016 3654.5102
2016 3753.344
2016 3851.848
2016 3944.771
2016 4041.79
2016 4133.79
2016 4229.73
2016 4328.11
2016 4425.40
2016 4522.51
2016 4621.41
2016 4723.61
2016 4822.40
2016 4920.70
2016 5022.50
2016 5127.20
2016 5226.66
2017 124.96
2017 222.521
2017 322.17
2017 424.910
2017 525.918
2017 6233
2017 731.2351
2017 840.4880
2017 953.8150
2017 1065.347
2017 11111.3124
2017 12110.79
2017 13221.32623
2017 14184.81017
2017 15172.5381
2017 16120.8143
2017 17115.393
2017 18126.764
2017 19144.726
2017 20171.5171
2017 21420.1
2017 22505.9290
2017 23272.9307
2017 24297.9139
2017 25238235
2017 26126122
2017 27129.6156
2017 28103.781
2017 29109.325
2017 3083.364
2017 3173.950
2017 3262.663
2017 3356.965
2017 3464.662
2017 355626
2017 3644.37
2017 3737.725
2017 3837.731
2017 3933.917
2017 4030.520
2017 4130.56
2017 4230.11
2017 4330.61
2017 4430.21
2017 4527.40
2017 4624.90
2017 4725.70
2017 4825.50
2017 4921.93
2017 5025.10
2017 5133.22
2017 5232.648
2018 129.15
2018 227.270
2018 325.923
2018 431.8143
2018 534.460
2018 631.2143
2018 733.1262
2018 838.3217
2018 933.584
2018 1058.91054
2018 1183.3237
2018 1266.742
2018 1378.58
2018 14126.1330
2018 15263.23709
2018 16540.14398
2018 17257.8380
2018 1823145
2018 19293.788
2018 20204.9120
2018 21607.4661

Early in spring around the beginning of April, an increase in sales of hay fever medication can be seen. This is also the period in which pollen of certain trees such as birches trigger allergic reactions. Grass pollen appear later in the season, which is also the time of year when the highest sales peak is recorded. Although the grass pollen count is not extremely high, many people suffering from hay fever are sensitive to grass pollen, which may explain the sales peak. Sales figures are therefore not always directly related to the pollen count in the air; sales are primarily related to the severity of the symptoms experienced by hay fever sufferers.

Figure 2 shows that the hay fever season started slightly later this year compared to 2017. Interestingly, a high sales peak was nevertheless already recorded in April of this year. GP visits on account of hay fever are displaying a similar trend (source: NIVEL surveillance). This peak may be related to the warm weather last April, which caused the release of many tree pollen into the air.

 

 201620172018
Mar 934.953.833.5
Mar 1065.965.358.9
Mar 1195.3111.383.3
Mar 1273.4110.766.7
Mar 1392.4221.378.5
Apr 14134.7184.8126.1
Apr 15228.4172.5263.2
Apr 16179.9120.8540.1
Apr 17108.6115.3257.8
May 18326.3126.7231
May 19373.3144.7293.7
May 20182.9171.5204.9
May 21259.7420.1607.4
May 22510.4505.9
Jun 23561.1272.9
Jun 24159.9297.9
Jun 25142.1238
Jun 26113126
July 27135.2129.6
July 28119.1103.7
July 29123109.3
July 3088.483.3
Aug 3168.773.9
Aug 3262.162.6
Aug 3367.756.9
Aug 3465.164.6
Aug 3557.256
Sep 3654.544.3
Sep 3753.337.7
Sep 3851.837.7
Sep 3944.733.9

 

Last-minute purchase

Data further show that people tend to purchase medication only when the pollen are released into the air, rather than stocking up on medication beforehand. It does not look like people only purchase medication at the beginning of the season for long-term use. In general, there is a clear trend that when pollen concentrations increase, sales increase as well, even later on in the season. In short, sales data of hay fever medication obtained from chemists seem to provide a fairly accurate picture of the duration and intensity of the hay fever season.

 

Explanations

CBS obtains transaction data from a large portion of the pharmacies in the Netherlands. The data are more commonly used as input for the consumer price index. In this collaboration, pharmacies have indicated that their data may also be used for statistical research purposes. Weekly sales data of around 30-40 different products used to alleviate hay fever symptoms have been used to produce the hay fever index. The turnover index is not intended to show the total sales volume of hay fever medication in the Netherlands, but to provide more insight into the development of the hay fever season and times when consumers purchase medication.

 

Feedback: 

We would like to know your opinion on this beta product and its potential applications. We are open to ideas on how this social phenomenon can be described more accurately using new data sources. Please use the form below to submit your feedback.