This reference is from 2009 and it has really changed the way I’m looking at all of this.  What they maintain in their article is that patients with seasonal allergic rhinitis and atopy in general have too much parasympathetic input, ie too much “rest and digest.”  How I missed this whole body of research is beyond me.  Full article here.

Their summary of pertinent HRV parameters.

mong them, RMSSD, SNN50, and PNN50 primarily reflect
parasympathetically-mediated changes in heart rate (Kleiger et al.
1992). The other time-domain variables reflect a mixture of parasym
pathetic, sympathetic, and other physiologic influences. We used
power spectral analysis of heart rate with the parameters of low fre
quency (LF: 0.04-0.15 Hz) which is related to baroreceptor control
and is dually mediated by vagal and sympathetic systems, and high
frequency (HF: 0.15-0.5 Hz) band reflects respiratory sinus
arryhthmia and, thus, cardiac vagal activity (Akselrod et al. 1981;
Pomeranz et al. 1985). Also the most indicative parameter of LF/HF
is used for assessing the autonomic balance.
Tohoku J Exp Med. 2009 Nov;219(3):187-91.
Cardiac autonomic imbalance in children with allergic rhinitis.
Tascilar E1, Yokusoglu M, Dundaroz R, Baysan O, Ozturk S, Yozgat Y, Kilic A.
Author information

The involvement of autonomic imbalance has been reported in the pathogenesis of hypersensitivity reactions. Allergic diseases are more frequent in children and some of predisposing factors may be changed according to the increasing age, but the involvement of autonomic imbalance has not been investigated in pediatric population. In this cross-sectional, case-control study, we evaluated the autonomic system by measuring heart rate variability (HRV) in pediatric patients with allergic rhinitis. Thirty-five pediatric patients with allergic rhinitis and 36 healthy children (mean age 11 +/- 2.7, and 12 +/- 3 years, respectively) were enrolled in the study. Age and gender were not different between the groups. The diagnosis of allergic rhinitis was based on the history, symptoms, and skin prick tests. Participants with acute infection, nasal polyposis, bronchial asthma, and any other medical problems, assessed by history, physical examination and routine laboratory tests, were excluded. Twenty-four hour ambulatory electrocardiographic recordings were obtained, and the time domain and frequency domain indices of HRV were analyzed. We found significant increase in calculated HRV variables in children with allergic rhinitis compared to controls, which reflect parasympathetic tones, such as number of R-R intervals exceeding 50 ms, root mean square of successive differences between normal sinus R-R intervals, the percentage of difference between adjacent normal R-R intervals, and high frequency. These results indicate that HRV is increased, which implies sympathetic withdrawal and parasympathetic predominance. We propose that autonomic imbalance may be involved in the pathophysiology of allergic rhinitis in pediatric patients.